If you mean what some posters often say, that "we don't know what made the cops angry before the video started", then that is no point at all.
When cops get busted for homicide or beating a man into the hospital or even to death without having to, or framing someone, then it really doesn't matter what annoyed them and led to their criminal act.
BINGO!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! If I am REALLY mad, and beat the crap out of somebody, I don’t get to say, “It’s okay; I was REALLY mad.”
In my situation it took a bit before I decided I better film this guy this don’t seem right. You never know what might happen. Legally if a cop encounters a mouthy person he cannot arrest over that. The charge must be valid and there must be probable cause.
LEO can arrest an individual for littering or jaywalking but it must be witnessed. After that all bets are off.