This just goes to show that when you have those "police brutality" videos where police are rougher with a suspect than seems necessary, they're actually using reasonable force. The officer got punched in the head multiple times and the suspect was holding a weapon, looked like a mini-maglight or something that he later dropped. He still kept hold of the suspect until backup arrived, even when he was semi-conscious and bleeding everywhere.
Police officers get in that sort of situation all the time. They're tough bastards, all of them because they don't get to back down when it's a fight, they have to take the aggressor into custody.
If you think it's funny then you're a dickhead and a coward.