[GoshisDead]

A group of people and a governed society isn't the same thing, once a group of vigilantes usurps the vengeance power of the law they have become separatists. A community's code of conduct is normally in line with whatever the law is, in "democratic" nations and societies. Vigilantism in the example you stated has an offender who probably broke the law, a law that was in line with the societal norms. It was when the law failed to deliver the retribution expected that the idea of vigilantism came to be. The vigilante in this case is doing what the law was designed to do but didn't. The possible injustice is that the offender does not get processed by the law which is also designed to keep innocent people away from vigilantes. So in a way yes, the fear is that someone will do something to you because you broke a community code of ethics, but it is more that one person or a mob, which in practicum is one person, get to decide your fate.