I don't think the police are the same everywhere, not by a long shot. Perhaps you've had bad experiences. However, in some places, the police, here including sheriff's departments, let some people get away with just about anything and at the same time, are constantly harassing certain other groups of people. Yes, it's a form of social control, to be sure, but you can't simply blame the police. It's one group of people doing their best to control and maybe even eliminate another group of people. Nothing new about that. It even happened before there were police. Often as not, it is also sometimes a case of a minority trying to control the majority. The police are usually in the middle. I'd have to say, however, that sheriff's departments in places where there is no police department, can be a little different, sheriffs always being an elected office.
So what is really happening? The truth is, I think, that a lot of people are opposed to public nudity, like it or not, for whatever reason. So don't blame the police. They are not the sworn enemies of a free people. It is also difficult to accept that people will accept most anything instead of anarchy, which is some people's idea of freedom. These days, it seems like a lot of people in a lot of places are perfectly happy to live in a dictatorship. I mean Russia, of course.