We should combat crime using methods that do not lend themselves so readily to abuse. A legal system exists for the purpose of punishing crime. Mob vigilantism has proven throughout history to be dangerously unjust.

Don't get caught up in your superhero fantasies and think that they can be applied to the real world.

In this one case. However, the methodology is still extremely dangerous to use. The Salem witch trial methods would still have killed many innocents even if witches did exist. And that's what is going to happen here.

Someone moderately clever will post horrifically offensive content under someone else's name, then "catch" the designated offender and post their info and purported crimes to social media.

The general idea is that people will hear the story, learn from it, and then not take the risk that the same will happen to them.

It may not be the best strategy, but historically it has had some degree of success.