Why security can do not good

[Technature]

is it because it is hard to tell the difference between a traitor, a vigilante, and a violent dipshit?

Basically.

The vigilantes and assholes can be just as problematic, and at times, murder happy as the bad guys.  Pretty much the only difference is Vigilante's admit they did a bad thing, but ask for a lighter sentence because, hey, that guy was kind of building a can bomb and it might have gone unnoticed if I didn't do anything.