According to the driver's Facebook page, he was turning right at a green light when this Virginia state trooper pulled out in front of him, turning left from the opposite direction, in an unmarked car. When the guy made an exasperated gesture, the cop pulled him over and ticketed him (for an inspection violation).
From the conversation, it doesn't sound like there's much disagreement over what happened. The disagreement is over the law. The cop seems to think that motorists have an obligation to stop at green lights before turning right. Or at least they do when an unmarked police car is turning in front of them.
Score one for smart phone video.