Re: Those 300,000 lives
You make a good point. Many intelligent analysts have made a similar case about both the causes of the Civil War and the eventual demise of slavery, so maybe the Civil War is a bad example for what I'm trying to say.
Like you say, I too firmly believe that slavery would have died out on its own, certainly when the first mechanized farm equipment hit the fields in the North. There is no way that manual farm labor, even free, can outcompete a machine.