I think it has to do with authority, like there's always going to be someone in a higher position than you.
This is going to be debatable, no doubt, but just for the sake of explanation, I'm going to say that Johnny's pretty low on the ladder of authority. Now take a look at the cops. They try to arrest Johnny and put a stop to his fun and they wear badges and the like. Then take a look at Stubbs. He tries to do the same, stopping the fun of whatever political party he opposes, or whatever, politics aren't my strong point. But yeah, he wears a suit and tie, compared to the cops, who wear badges. So in that context, which I'm assuming is the literal context of the phrase, there's always a "man", but he wears a different uniform, with "uniform" standing in for their occupation or place on the ladder of authority.
Not only that, but when you hear Johnny use the word "man" in that sentence, the old allusion of the saying "the man" being used by hippies, bikers, people stuck in the 1960s-1980s, etc. being used to refer to the head of "the establishment", or whatever they're protesting against. I'm probably overthinking this way too big, but that's just my take on the meaning.