Well, it was pretty fucked up he just sat there and punched him in the face/head but like someone said, he wasn't hitting him that hard cause he never really appeared to be knocked out. But I feel like its fight-ethics (at least boxing, mma, most other non-shit heads) to stop punching a person in the face when they're defenseless on the ground.
That being said, the kid did start to try to fight back but the kick/knee to the head was pretty unnecessary. Kid who did the punching is luck he's not in jail for a few years and lucky the kid who he was punching had a thick as skull and wasn't a bitch about it. The dude could have easily pressed charges, but the dipshit who almost beat him to death got lucky, but again, the dude got up after and walked away so he obviously didn't do much damage (or the kid didnt have much to damage).
Overall, I'm surprised no one came in and pulled him off when he was just whaling on his head. Both are lucky that one isn't brain dead and one isn't in jail. Bet they'll get a ton of youtube hits lol