He's a moron for not complying, but the punching was definitely unnecessary. They had the manpower to force him down without that. They were obviously just pissed that he was acting like a pissant.
Why do they need to force him down? He wasnt doing anything. Why do people feel that just because theyre police they can command people what to do, even if they have committed no crimes?
I don't know in that case. Maybe the cop thought he could turn into a rogue element if left unattended. That may be a dumb idea for the cop to have, but it's a simple enough request and it likely would not have taken very long. The police have to deal with a variety of factors during an investigation, so they'd like to have everything under control. It's not like "sit down over there" is a violation of his human rights. When you don't follow their requests, then you do turn into a rogue element and stuff like this happens. I think they took it too far and should have been punished considering they knew for sure that he was not armed, but following police instructions is the key to not getting into shit like that in the first place.
So would you be okay with them handcuffing him? Would you be okay with them telling him to sit and how to sit? Cross your legs? Lay on the ground? Stand against the wall facing the wall? Dont do these things and get your ass beat?
Fuck that shit.
If the cop is acting with proper judgement and they think it is necessary for public safety, yes. As long as they have a probable justification for taking those actions, they have authority to do so. I think they had every right to ask him to do that. I think they had every right to use force when he did not follow their instructions. I do not feel they had the right to use the method they utilized.