Be sure to read the rule before you leave

I'm not trying to be snarky or pedantic when I ask, what is a cop to you? Would you consider a cop to be any enforcer of a formalized state structure that has a monopoly on violence? Anyone who takes on an armed role for organized community defense?

It's very easy and sensible to go with ACAB for the US, but when we're talking about for example a communist vanguard in defense of a working class state socialist project, if we just say it is identical fundamentally, then what are we left with to defend against the violence of the colonizer, imperialist, etc.? Or if we were to say it's bad when it's a "dictatorship of the proletariat", but good if it's community defense, what constitutes the difference and how is the 2nd one strong enough on a practical level to achieve liberation?