"For the cost of one extended colony on another world, you could fund a complete robot space program visiting many worlds, even making repeat visits if they turned up something really interesting."

First, NASA should not have an extended colony on another world. Second, we don't need NASA exploring many other worlds. Yes I would like NASA to explore Ceres and I'm happy they are going to explore Pluto, and more importantly we are about to get more information about Mercury.

NASA's job isn't to exam each rock in this solar system or, at at least at this time, to mount mission to some other solar system.

I mean if NASA were to explore every rock in the solar, couldn't the tax payer says, well, that nice, are we done yet?
And can't they say right now, aren't we done yet? Why not save some of this exploration for future generation- they too might be bored.

The thing is that the America public wants to go into space. That is the only thing that gets NASA any of it's funding.

Have some President who wants to be elected tell the American people that they will never go into space.
What the compulsion of needing to lie? Let's see who going to vote on that idea.

Why are the Chinese doing a manned program?
Just stupid?

In a thousand or 10,000 years humans will be living on the Moon and elsewhere. Maybe the country called America with weird constitution which defines that particular nation will not even exist, but it will probably happen. Just like it's likely at some point there will be nuclear weapons which are used to kill people. These types of questions not really a matter of "if" but "when".

So, I think America should continue it's manned program rather than get rid of it. I don't think you could get rid of manned program- I'm not worried about it.

One way to look at it is that NASA, though it waste tax payer's money; as compared to other government programs, it's peanuts in terms of costs and do a lot good than compared to these other government agencies.
But my point is NASA budget is peanuts, if there was political support for more robotic exploration, why simply get the political will that will add more money for the NASA budget for more robotic exploration. Let's add 25% to NASA budget for robotic exploration only- something like 25-50 cents per tax payer. This kind of increase gets you all the robotic missions you could probably desire.

Or if robotic missions are so desirable why don't other nations get more involved with doing this. Why are other nation involved with the US led manned program? Why are the Canadians so stupid? What is UK doing in this regard? Why doesn't India and China show us how to do it the right way?

My biggest complain of NASA is it wastes time, not money.
It's essentially puttering around. I would like to see NASA budget double- and I not supporter of government spending. But by doing the right things we would be practically "forced" to significantly increase NASA's budget.

So, it boils down to, is there anything worth any effort in regards to to Space.
To me, it's obvious.
It's like asking was buying Alaska worth it? Mars at a government cost of 1 trillion is cheap- and I'm not a Mars fan, in the sense that our present focus is to go directly there without going to the Moon.
Mars might be worth it, but it's not the most valuable prize to seek. For instance I think it's more profitable to capture the rocket fuel market- and that is fairly minor. Far more valuable would be earth's electrical market.
Now, this is business angle more than government angle, but it is a governmental angle to think in terms increasing GNP. And it is a governmental angle to think in terms of being part of establishing laws and governance in regard to all activity in the Space environment.

Now, I don't like colonies in space angle, oppose to establishing relations with at the moment non existing nations in Space. So the model of "pax American empire"- we can have some say in how things develop in space.

We would probably do a fairly bad job of it, probably outlaw nuclear weapons, and ban smoking or something.

Ok, one way to look at it, is to ask, for Europeans was finding the New World and developing the New World, worth it? For the Brits they might have some regrets, but that it pretty shallow thinking, a bit too nationalistic- and what did they really get from having the British Empire in comparison to having an American ally.
Or another way to say this is what did China lose by not discovering the New world and developing it. The chinese burnt there explorational vessels because of costs involved.

It's nothing to do with the gold, it's everything about transforming people- who do happen to like gold.