Who is the Social Darwinist?

President Obama, in the midst of another temper tantrum, called Paul Ryan's budget "thinly veiled Social Darwinsim" last week during a press conference. (I keep waiting for his serious, intemperate and professorial responses to anything in which he disagrees the slightest.)  Rich Lowry has some thoughts on all of this:

If social Darwinism is merely the belief that the market is the best system for allocating capital and wealth, and that a free society will necessarily be an unequal one, then almost everyone in America is a social Darwinist. Even the president constantly pledges fealty to the market and doesn’t want to confiscate all of Mark Zuckerberg’s income. He is using social Darwinism as a free-floating pejorative for people whose policy preferences he doesn’t like, which is entirely appropriate.

And obviously if the policy is now opposed by Obama, it is bad no questions asked (even if, as Rich notes, he supported many proposals similar to Ryan's in his own budgets).

Rich also has an interesting aside that I always find worthy to note:  "In this respect, liberalism hasn’t evolved at all down through the decades: Seventy years later, it’s still the same witless insult, for the same reason."  For all the talk of Progress and "being on the right side of History" and being in-tune with the times, it sure is strange to still be clinging to political ideas more than 70 years old.  I thought the Democratic Party was the Progressive party?