I hate lynch mobs. ACAB and "fuck the police" are lynch mobs based on broad generalizations.
There is scientific data and statistics to show that black people and others are disproportionately targeted by the police. It's immediately obvious the police unions protects their own including some folks they likely shouldn't.
These are problems we should strive to understand and fix.
There is not scientific data showing that all cops (or even more than a minority of cops) are bullies out to treat everyone as a suspect or fetishize their next opportunity to beat the crap out of someone. That is an opinion and one that immediately shuts down any hope of a reasonable discussion about how two parties might move forward. Show me one scientific study where someone went "you're a bastard and you can go fuck yourself" and then got a constructive response... It doesn't exist, because people do not like being put into groups and told what their own individual opinions must be.