What would happen to someone playing junior cop legally?

One thing that always bugged me about the Zimmerman/Martin case was while actions might be legal they can still be ill advised. Focusing on legality rather than social convention, ignoring social cues etc

I mean like for example walking up to and questioning strangers, and then defending yourself when they respond badly. Chances are a few people will respond aggressively if you act like a junior cop to enough people.

Or say performing a citizen’s arrest on someone seen smoking a joint or urinating behind a dumpster or a hooker or john, most legal advice on CA I’ve seen is not to try it. It is pretty much a guarantee it will go badly.

I realize these aren’t legal everywhere, what do cops usually do with someone whose actions are legal but a nuisance and a ticking time bomb before someone gets hurt badly or killed?

generally call the cops and let them deal with it. Even cops end up in little scuffles with folks doing stupid shit like that all the time. Unless you are some epic grappling badass able to pin and restrain anyone without worry of you getting hurt or injuring the other party…probably stand a decent chance of getting your ass kicked.

[cop impression]
Go away before you annoy me enough to find something to cite you for.