This is magic. So the desk sergeant is having a bad night and he's feeling overrun, and that gives him the right to twist some poor buggar's arm off? I must remember that the next time I'm having a bad day, or night.

"The guy has indulged in bad, possibly dangerous behaviour. perhaps he has even uttered racist comments........."

I don't know how many times I have to say this. What the guy has or hasn't done has no bearing on the way he was treated. The appropriate punishment for bad behaviour, racist comments or whatever is up to the courts to decide. Have you never heard of the phrase "Innocent until proven guilty"?. Or would you prefer to live in the sort of banana republic where such behaviour by the forces of law and order is considered acceptable?

BTW. His arm wasn't twisted up his back because of what he had done outside. It was twisted up his back because the guy didn't feel well, and refused to co-operate until he was given a chair. What the hell was wrong with giving him a chair, for God's sake.