There are some RL versions of vigilantes and vigilante groups in a limited fashion. In the 70's or 80's there was a guy who shot two gangbangers in the NYC subway, it was reputed that he was inspired by the "Deathwish" movies and was fed up with the extremely high crime rates, I forget if he went to jail or not, but he was arrested though. Also there were the Guardian Angels, they never actually killed anybody, they weren't a comic book style superhero group, more like a neighborhood watch on steroids. Then there is FSU, which is a gang in Chicago and Philadelphia, they don't really fight crime so much, but they do consider themselves "straightedge" and they do like to pick fights with skinheads.
As for actual real vigilantes like you see in the comic books, I could see something happening. Say you get a lot worse crime in the 70's and 80's, perhaps without the situation getting better as it did in OTL. Add in more government corruption, which isn't all that hard to imagine(hell look at Illinois.) So look for crime to get so bad and the government to get so unable to deal with it that regular people are faced with a situation where taking the law into their own hands is the only way to protect themselves from crime. Also public support would be unimprtant in my opinion, but wouldn't hurt to have.