The issue is not the social function though, it’s flaws in some police departments. Even on the left, there are very few who actually don’t want police around serving the function of stopping crimes when they occur.
It's not a flaw in some police department, it is a flaw in the social order that manifests itself in abuses by numerous police departments, but the seeds of that are present in essentially all of them.
Expressing the violence of the state is much broader than stopping crimes when they occur.
