We invented rule of law and the ballot box to protect ourselves from each other. Yes it may be inefficient and may produce results we don't like, but once it becomes ok to murder people you disagree with, that legitimises killing anyone.
This word is doing a lot of heavy lifting in your comment. A parasite was terminated.
Put another way, how many Americans have cheered seeing Batman tackle an industrialist who killed a fraction of the number of Americans who die because they can’t get adequate healthcare? I strongly agree that gunning people down for perceived injustice isn’t anywhere we want to be but that means we have to actually fix the problems. Here’s a survey which found 34M Americans know someone who died because they couldn’t get healthcare, and 58M couldn’t get medication they needed – those numbers are very high if you want a peaceful society:
https://news.gallup.com/poll/268094/millions-lost-someone-co...