And why was Biden there? Simple...balance. The "handlers" knew that the picture of two black men ganging up on one white guy wouldn't play well.
The police officer hit a home run at his news conference and that's bad news for the professor. A true professional! The professor now has a tough act to follow.
It's easy enough to see, especially after some rudimentary investigation in to the background of the players at hand, that the professor is the one that was the race baiting antagonist, start to finish.