All very nice but before I get bog down; I will remind you of the question: "So, perhaps RL could explain what major policy issues differences [in America politics- among those that claim they are socialists, communists, Marxism, or "progressives"]. "

Now my point is not that Mary Anne shouldn't answer this for RL. But rather that Mary Anne didn't answer the question and instead chose to answer other things.

Anyhow, I'll go over some the points raised:

"Socialists believe that government should provide a certain basic level of support for individuals....in the economic and social sense. It's a form of paternalism that's compatible with political democracy, but it doesn't play well with no-holds-barred capitalism. The New Deal had some very prominent socialist initiatives, for the very wise reason that a little socialism will go a long way toward defusing radical Communism in hard times, which the US endured during the Great Depression and the Dust Bowl disaster. It was pretty obvious at the time to the people of the US that capitalism and its practitioners didn't give a rat's ass about most of them."

No Doubt the Socialistshave many fantasies. But what is fairly clear is the New Deal did not have much affect upon the Great Depression and could very well have worsen it. But we did get progressive income tax, of a kind that even Dems today would call extremely foolish:

"The Revenue Act of 1932 was the first tax law passed during the Great Depression (Revenue Acts, June 6, 1932, ch. 209, 47 Stat. 169). It increased the individual maximum rate from 25 to 63 percent, and reduced personal exemptions from $1,500 to $1,000 for single persons, and from $3,500 to $2,500 for married couples. The National Industrial Recovery Act of 1933 (NIRA), part of President Franklin D. Roosevelt's New Deal, imposed a five percent excise tax on dividend receipts, imposed a capital stock tax and an excess profits tax, and suspended all deductions for losses (June 16, 1933, ch. 90, 48 Stat. 195). The repeal in 1933 of the Eighteenth Amendment, which had prohibited the manufacture and sale of alcohol, brought in an estimated $90 million in new liquor taxes in 1934. The Social Security Act of 1935 provided for a wage tax, half to be paid by the employee and half by the employer, to establish a federal retirement fund (Old Age Pension Act, Aug. 14, 1935, ch. 531, 49 Stat. 620).

The Wealth Tax Act, also known as the Revenue Act of 1935, increased the maximum tax rate to 79 percent, the Revenue Acts of 1940 and 1941 increased it to 81 percent, the Revenue Act of 1942 raised it to 88 percent, and the Individual Income Tax Act of 1944 raised the individual maximum rate to 94 percent.

The post-World War II Revenue Act of 1945 reduced the individual maximum tax from 94 percent to 91 percent. The Revenue Act of 1950, during the Korean War, reduced it to 84.4 percent, but it was raised the next year to 92 percent (Revenue Act of 1950, Sept. 23, 1950, ch. 994, Stat. 906). It remained at this level until 1964, when it was reduced to 70 percent."
http://www.answers.com/topic/income-tax

Some history on Federal progressive tax:
Here Wikipedia tries to tie the idea to founding fathers:

"The idea of a progressive income tax has garnered support from economists and political scientists of many different ideologies. Adam Smith alluded to progressive taxation in The Wealth of Nations. Smith argued that "the expense of defending the society, and that of supporting the dignity of the chief magistrate, are both laid out for the general benefit of the whole society. It is reasonable, therefore, that they should be defrayed by the general contribution of the whole society, all the different members contributing, as nearly as possible, in proportion to their respective abilities." As an example of this, Smith advocated a progressive tax upon modes of transportation, writing: "When the toll upon carriages of luxury, upon coaches, post-chaises, &c. is made somewhat higher in proportion to their weight, than upon carriages of necessary use, such as carts, waggons, &c. the indolence and vanity of the rich is made to contribute in a very easy manner to the relief of the poor, by rendering cheaper the transportation of heavy goods to all the different parts of the country."
http://en.wikipedia.org/wiki/Progressive_tax

Of course the federal needs to have a miltary capability and of course local taxes were needed for roads and later even education- seemingly reasonable considering that there was arguably at high rate of people who couldn't read- not that public education has actually been very successful in this regard, but it seemed somewhat reasonable.

More tax history:

"The Civil War represented a watershed moment in the history of American taxation.
...
But the war grew increasingly costly (topping $2 million per day in its latter stages) and difficult to finance.
...
In response, Congress approved two new laws in 1864 that increased tax rates and expanded the progressivity of income taxation. The first bill passed in June upped inheritance, excise, license, and gross receipts business taxes, along with stamp duties and ad valorem manufacturing taxes. The same act proceeded to assess incomes between $600 and $5,000 at 5 percent, those between $5,000 and $10,000 at 7.5 percent, and established a maximum rate of 10 percent."
http://www.tax.org/Museum/1861-1865.htm

Ok, so during Civil War the govt was printing money at mad rate and this was causing inflation, so taxation was seen as solution to this. And it's true that taxation if you printing money like drunken sailors, will reduce inflation- it also reduces *real* economic growth. Prior the civil war the biggest problems the govt faced was surpluses in the government [they at the time were incompetent amateurs at wasting tax dollars- they lack the imagination neccessary to provide excuses that seemed reasonable to the public- besides once upon a time most Americans knew that taxation was equal to oppression and enslavement].

More history:

"I discovered that during this period, the political philosophy of income taxation was more fully articulated," Joseph writes of the 1890s. "This finding led me to believe that the social origins of the American income tax lay not in the twentieth century, as some might suppose, but rather in the nineteenth century." Fair enough, although that sort of backward glance might be cast even further: Many of the arguments resonating through the Capitol in 1894 were echoes of even older Civil War debates over income taxation.
But we all have to start somewhere, and Joseph starts in 1894. The income tax enacted that year, he contends, was designed "to shift the burden from the less wealthy to the wealthy." Tariff duties were distinctly regressive, and Democrats had been arguing for years that rich Americans should be paying more. Lawmakers finally agreed, imposing a modest, 2 percent flat tax on corporate and individual income. (Joseph points out, however, that the tax treated any net increase in wealth as a form of income, including inheritances and gifts.) The tax was not designed to redistribute wealth or restructure society. Rather, it was designed to redistribute the tax burden and restructure the revenue system. Still, it was an important triumph for progressive ideology."
http://www.taxhistory.org/thp/readings.nsf/cf7c9c870b600b9585256df80075b9dd/1fe74d7f2f033e738525701300527150?OpenDocument

Now, skipping something vaguely interesting.
Marry Anne continues
"The differences among these three, and their potential impact on American policy, is pretty plain to me.

Marxism is a philosophy. It's fun to talk about. It's an academic exercise that has political impact only when one attempts to put it into practice in government."

Oh, I can see the fun. Marxism was written by uneducated fools, it's short enough that moron can scan through it's pages in few minutes. And is so poorly written that in some respects it's like reading from the bible. Oh tons of fun for the kiddies here. And very inspiring to people who want to write anything, it's so dissimilar to any seriously written work.

"Communism is that attempt, one which seeks to establish absolute economic and social equality in theory, and so requires the iron hand of dictatorship with its implicit political elites, violence that comes with forced participation, and social hypocrisy, in practice. "

No you got it completely wrong. Communism came from an incomplete understanding of the Wonder of the World- America. It was an attempt to fast track social evolution. It's not strange that it failed. And Russia Communism was an attempt to continue policies of the previous regime- only problem was the guys trying continue this social advancement were murderous, lying, cheating, ignorant ego manics. Russia advancement was mostly due to policies started by the Czars. Terrorism ended the Czars and gave birth to Communist Russia- the leadership of Communist Russia were good at one thing: propanganda; a similar trait of our modern terrorists.

"Socialism takes some of the aspects of traditional religious charity and attempts to codify them and make government the agency that will deliver a certain amount of safety to all citizens in the form of minimum living conditions and care. Socialism has been with us for thousands of years. Current socialism takes what used to be called religious duty and noblesse oblige and tries to put it in the context of modern rationalism and political democracy. It's more about equal opportunity -- think "20 acres and a mule" -- than it is about the ideologically pure equality espoused by Communism."

Well, I agree that Socialism has been with us for a long time and associating with established religion is a good point. But the established christian church is 1000 or at most 2000 years. Beyond 2000 years it's fairly murky. Of course you could tie it's roots with tribalism and therefore get into the thousands of years range. Whereas Capitalism is a bit more spoty in regards to it's lineage. It suggest that you just look at anywhere in history in which their "golden ages" and free trade that would good place to start. The silk road and it's history and ancient China for instance.

Marry Anne:
"Progressives are social reformers. That comes from American history, circa the turn of the 20th Century. The aims of Progressives have been many and varied, and some of them have been better or more important than others..."

Of course the Progressive started early and they were mostly about "economic freedom". They correctly saw that tight money supply was hindering and slowing economic growth. They saw Silver as better choice to tie the value of money to. Of course the real genius was tying money to debt- really much more unlimited in terms of supply- but that required a rather, how shall say, cynical view of the world:)
Whereas the Progressive of Old were pretty optimistic- radical, but that was in a more civilized age. Though the dollar based on debt is based on the Progressive values, they probably would seem that as too radical- maybe even demonic.

Marry Anne continues
...Humane treatment of prisoners and of the mentally ill, and women's suffrage are three I would consider worthy; Prohibition, not so much. Modern Progressives are more likely to be aligned with civil rights movements and environmental concerns, because this is where they perceive a need for reform. The effects of Progressive activities on American policy are also pretty plain to me. I can vote."

All this isn't really much to do with progressive movement- it's sort of similar to Black Panthers tying in things like feminist movement goals.
This values are much older than progressive movement- but aligned to socialism of the religious orders.

Marry Anne continues:
"Personally, I think that the workers owning the means of production would be a good thing. It means that they would have an overriding interest in the success of the company, as their jobs are on the line, and that they would profit from its success in a much more real way than mere wages and benefits..."

There is of course nothing stopping any group people starting their own business and running the business any way they want- that's capitalism. But problem is when you want prevent someone from offering someone else money to work for them. Or you want to take a business which is owned by a person[s] or public ownership and give this to the workers. It's like you want govt to steal someone's property to give it the gardeners and housekeepers. You oppose a gardener getting a job that he/she chooses to have- you imagine it's demeaning to do this kind of work. Now, it can be demeaning- especially if it's caused by those who regard the job as something only a sub-human would do. The problem isn't the work itself, it's whose who completely clueless about work because their parents "love them so much" that they want to give their children a priveleged life [yeah, really dumb].

Now, of course the other aspect is you imagine people aren't paid enough money and this is unfair. The solution to this is you should support things that increase wealth in general and lower barriers for people to start their own business. A good way to do this is teach people how to run businesses- below the high school level. In other words, instead filling their heads with unworkable socialism, teach kids what capitialism is. Don't brainwash them into thinking it's evil. Teach them that hard work is good, and encourage all students to start a small business of some kind. And yes most businesses will fail- not be very profitable or go bankrupt- that's life, you can learn from mistakes.

Marry Anne continues:
"...It also means that they would be willing to maintain excellent working conditions, and to look out for the local environment, since most of them will live there. This is unlike our current system in which people who live removed from the means of production and its effects make money owning the company, which then answers more to their interests than to the welfare of the workers. But that's neither socialism nor Communism, but anarcho-syndicalism. Anarcho-socialism will only work if one makes it a contractual condition of employment that a worker become a stockholder, and that all stock is sold back to the company once a worker leaves the company, so that only employees own a piece of the company. I know that some conservatives scoff at this, saying that it would be impossible for a company to be run efficiently with all those people trying to make their opinions known. I suppose they have a point, if you think that the people are incompetent to govern themselves."

I'm not going to scoff, I say if you think it will work, and if you think others don't understand this well enough for it to work- then you should do it. If it works, you will be rich or maybe if you like: loved by millions or billions of people.