ACAB is universal because "cops" supposes a class of professional law enforcers. Police are a technology of social control, but they're not the only method of enforcing social norms and mitigating anti-social behavior.

As a thought experiment, imagine every member of a community was trained in community self defense, deescalation, mental health support, and other skills for nurturing a safe and healthy community. Every member of the community takes turns being "on call" or walking around the neighborhood in a community support role. There are no cops, instead the entire community is performing the roll of community defense and community nurture on a rotating schedule. There's no opportunity to accumulate power, there's no hierarchy. If the community needed assistance with a serious crime like a murder they could call in professional investigators or detectives with specialized tools and training, but the findings of those investigators would be turned over to the community for action.

There are alternatives to police. Police aren't necessary or inevitable. And because there are better ways all cops are bastards.