A few days ago Jonathan Chait asserted that modern conservatism is "doomed" because it is "rooted in white supremacy." The first claim may or may not be true, but there's little doubt about the second. Whether it's the Senate minority leader claiming that America should have remained legally segregated, a beloved cultural figure fondly recalling how happy black people were living under lynch law, a presidential candidate calling Barack Obama a "food-stamp president" or a campaign surrogate calling Barack Obama "