Well, putting his hand on a cop after being given a command is a show of "defiance". They'll probably get excessive use of force.
My opinion, they ramped up'ed their level of aggression too fast. They may have had an APB on a suspect and he matched that description. Considering his location, that would have prompted them to pull over to talk to him. But even then, if he put his arm out to the chest of the cop, all it would have taken was a simple <secret jiukitsu move> and he would have had him under control without needing to use the baton.