It happens everyday.
During a fight, no. After the guy who was hit had four of his friends tie the other guy's hands behind his back and hold him up, yes.
I have seen the video and it's disgusting, this guy might make a great salesman or customer rep. or whatever, but he should not be in law enforcement.
Again, what you describe is not "law and order conservatism".
Try this scenario on for size genius. Say you are out at night and some guy attacks you for no reason and cuts your head open. You get 4 of your friends and jump on this guy and cuff his hands behind his back. Then you slam his head into a car and punch him in the head.
If you think you won't get prosecuted for that you're living in a fantasy world.