I have a couple of cop friends and they'll be the first ones to say (off the record anyways) that police frequently beat the shit out of people.
The thing is, when they beat the shit out of a scumbag everyone loves it (including me, I'm guilty of that as well) but sometimes they catch innocent people as well.
In this video there are more then enough cops to restrain that kid. There was no reason for all of them to beat him. Their adrenalin was running pretty high and I'm sure a few of them have been reprimanded (no donuts for a week)