The guy threatened the cop's position as alpha male. That's auto-"cuffing/tasering/punch in the face/nightstick up the ass/shot in the face" in this country. Being black just speeds the process along a bit more.
Here's "the message": when interacting with southern cops, be sure to be as subservient as possible, don't "cop an attitude", and do EVERYTHING they tell you to do no matter what.
I had a Raleigh, NC cop almost shoot me (well he said he almost shot me) for approaching his car to ask for directions.