Woah there mate, let's maybe take a step back. I think we got off on the wrong foot. We're certainly talking past each other it seems.
My original goal was to caution against turning this into the very same green versus blue fight that we see all the time. I was tactfully trying to avoid criticising you for asserting that the police are little better than the fringe lunatic element on the blue half of our divide. In my view this is unsubstantiated and a little absurd.
Judging by own research on and experiences with the police in this city are excellent at their job, and have a lot of experience of handling this type of crowd.
Now, to OP's specific incident. I shouldn't have to say that I agree that being threatened with arrest for being assulted and racially abused is a bad thing. That happened here and it is disgusting. That is not how policing should work.
However, the actions of the police in this single incident does not provide sufficient evidence to characterise the police force as mostly loyalist thugs. In my opinion that is part of the tribalist problem we have in this city.