Youre misunderstanding that quote i think. Its not that theyre refering to themselves as police. Its that theyre talking about getting user info from @dan and @ned calling the actual police on people. For something said on the internet.
Not that its likely that they would have a cause of action for criminal prosecution. But do you really want to explain to detective whatever that disagreeing on the internet isnt a crime.
In my naive approach I didn't take the literal meaning, it seems. Well, that is poor indeed.