It’s one thing to say “given there will be crime, and some criminals are violent, cops may have to be violent sometimes to stop criminals”. That’s a pretty bloodless analysis.
Let’s get to the fun part: “if cops perceive someone to be a criminal, how violent will we allow them to be, relative to how violent the perceived criminal is?”
In the case of the cops assaulting that vigil for Elijah McClain (it was a peaceful gathering with people listening to a couple violin players) I’d argue that the cops were perpetrating violence at a level about 100x relative to the people they were trying to police (even if you consider that folks may have been “yelling mean things” at them).
Personally, I would consider 1.1x acceptable, maybe 1.5x in some situations. And so every time I see cops blowing through that threshold and being even 5x or 10x more violent than the people they’re policing, I perceive that as a massive injustice, I think those cops should get fired, and I get pretty angry.