Mob justice is how “that evil witch walked across my fields and now my harvest is rotten” turns into lynching innocents. If I can grab someone and accuse them of something and other people jump in on good faith that I’m being truthful, there’s a risk that they’ll end up beating up an innocent if I wasn’t.

What they should do at best is hold the other down for professional truth-finders to come sort out whether the accused actually is an asshole or whether I’m the asshole trying to frame them.