to Biden "you can't do this to black media" when Biden wanted to end interview. The black host just joked for his purpose not to end the interview, not really accused Biden of mistreating black media. Biden replied by saying "white media...." which is also a joke for his desire to end the interview. "Black media" and "white media" here all are jokes with each has its true intention. But nothing wrong with this kind of joking. At this moment we can clearly see that black host and Biden established a chemistry under which Biden made "You ain't black" joke later.
I think your black friends. like me yesterday, just saw a short version of video, didn't see the whole video, therefore didn't realize this is a joke from Biden.
BTW, I just listened podcast of my favorite blogger when I drove earlier, the great Scott Adams. I believe many conservative posters here read his articles in last 4 years. He thinks this is a A+ joke from Biden.