To be completely blunt I think he is trying to say there is a correlation between the density of African Americans and the success of college programs in those areas. And lets be 100% honest, that those areas do have a larger number of great athletes then the areas of the map that are not as dense with African Americans. I don't think he is trying to be racist, but I can see where it totally came across that way.
Programs in that area are more likely to keep those athletes, due to location to those athletes. We always harp on our 500 mile radius, well you can bet they are trying to do the same. Hell look at Miami back in the 80's and how they tried to win "The State of Miami". It's no different. Again Toe's map is showing that their is a correlation between the density of African Americans and the success of programs in those areas, and that if the map was flipped and the density of African Americans was much higher in the north than in the south then it's a reasonable assumption that the programs in the north would be winning more Championships then the teams in the south.
Again I don't think he is trying to be racist, but instead just pointing out what he believes to be the reason for the south's success