The point when he was in handcuffs on the ground would have been where he should have waited the situation out kept quiet and not talk to officers "how he appreciates their service." or enquire if their actions where "standard protocol". That is just asking for trouble.
Yes, physically removed from the immediate situation which is treating an accident victim and the first responders don't want to figure out whether the dumb white kid who keeps sticking around is an off-duty EMT.
He absolutely should have been physically removed from that particular situation since he wasn't leaving on his own.
This doesn't mean he should have had his hands stepped on or been put in solitary to teach him a lesson.
Stop making excuses for bad behavior!