They bounce off of a piece by journalist Juan Williams and from the information I saw from The State of... blog, the divide seems like more of an income, economic, and values divide than it could be a racial divide. The piece itself indicates that of those blacks polled, it is those who are undereducated or poorer who don't see blacks as the same race.
Let me quantify undereducated. The quote that I saw of Juan William's report mentions specifically referred to blacks who only got their high school diploma as opposed to those blacks who went to college and got their degrees. Of coure to quantify income it wasn't specified what was meant by low income but those surveys who see blacks as having common values make more the $100,000/yr.
The State of... never linked to it but here's the article I assume they blogged about. Have a read courtesy of the Washington Post.