Voting Red With Your Feet?

Using data from the new census, Walter Russell Mead considers black flight to the south:

The failure of blue social policy to create an environment which works for Blacks is the most devastating possible indictment of the 20th century liberal enterprise in the United States. 

Helping Blacks achieve the kind of equality and opportunity long denied them was more than one of many justifications for blue social policy: it was the defining moral task that has challenged and shaped American liberalism for the last fifty years. The Census tells us that in the eyes of those who know best, these well intentioned efforts failed.  Instead of heaven, we have hell across America’s inner cities. 

Yglesias differed earlier this month:

[T]he basic dynamic of weak job opportunities in the midwest and no affordable housing in the northeast applies regardless of skin color. What’s more, this is really not a reversal of the Great Migration in any meaningful sense. Texas wasn’t a major historic African-American population center and it strains credulity to describe Miami as part of the south. If black people start leaving Chicago to move to rural Mississippi that be a reversal, but this is the same sun/permit-driven migration that everyone’s doing.

But these two explanations are not mutually exclusive, are they?