Maybe someone (OP or other saying pro-vigilante) should actually cite some real world examples of this working or being needed.
Yes, there is Batman, Punisher, etc. but the only time I can really think of vigilante being 'good' or necessary is 'wild wild west' type scenarios (if it ever actually happened 100+ years ago) where the villain is the 'law' with money, power, etc. and the lone ranger brings him down.
Isn't the main point of vigilantism getting 'justice' in situations where 'justice' cannot be given due to some circumstance? If a criminal is getting death penalty, (or agreeably suitably punishment) then what is the need of 'lawless' violence? Only 'need' would be if the law wasn't on your side or, for some reason, not able to prosecute a villain... but even that is questionable.
C