Yeah, the whole vendetta thing certainly is "funny" /s
That's exactly how people defending "righteous causes" end up being trolls and harassers themselves.
Society has to be built on some form of punishment for harmful behavior, the issue is what is that punishment? Should these people go to jail? I don't think so, should they be punished in some way as a method to teach them a lesson.
If they should be taught a lesson, the favorite of most people is, "see this is how it feels." Steal and we'll take something from you, bite and be bitten, hit and be hit, eye for an eye.
The main issue is that this often (IMO) doesn't actually teach what you want. It teaches that if you bit this person they'll bite you but it doesn't address the deeper issue with the original action. Which would require therapy and a support network. All of which is time consuming.
And why would we waste our time on someone who is being punished, lets just throw them in jail because hitting people in public is wrong.
</soapbox>
In the end it's human nature to want to teach a lesson in the least amount of effort to make themselves feel better, and the easiest way to get your bang for your buck it to punish people with the same punishment they received, often times things are more complicated then that.
Sorry I went way overboard, but I've seen this time and time again, and as I have a biting, kicking, hitting 19 month old kid now, I've been looking at how do you address this without becoming a troll and in my case a toddler... I want my kid to grow up not for me to become less mature.
When one misuses their abilities to harass/intimidate others, some of their liberty should be taken away, wouldn't you agree?