It's possible that the race thing has legs. Maybe not the "black people don't like the cold" part, but possibly the "A percentage of black people are more comfortable in concentrations of people who look like them" aspect of the argument.
But ultimately, I think folks (of any color) are comfortable in certain environments that are similar in some ways to the place they were raised.
For instance, I'm from Oregon but hated Purdue, and the entire midwest, so I transferred to Colorado where I was quite comfortable. I don't see most folks that grew up in the Rocky Mountain region as being particularly comfortable in the South. I know I'm not comfortable there, as I've stated before.
But that goes two ways. I don't think Southerners are always content in Boulder. We've lost football players in the past because they just weren't feeling it there. Similarly, our student population doesn't reflect a strong Southern represenation.
If we're willing to make an argument that there is a higher concentration of quality athletes in the South--many of whom are black--than say the state of Colorado, than...I think I lost my train of thought here....but you guys get what I'm trying to say.