Why gun vigilantism is so problematic

This is Joseph.

Consider this tweet by Josh Marshall:

Or this one by an internet commentator:

In both cases you have an issue with demarcation between what is a lawful use of self-defense and what is an active shooter. Let us be blunt. There are definite cases of criminal mass shooters. There are also cases where actual law enforcement officers abused their positions to commit crimes. How much worse does it get when random citizens can start enforcing laws in a chaotic situation? 

The classic example is an active shooter at a movie theater. It is dark. It is crowded. It is hard to see and hear anything with the gunfire and smoke. Now imagine 20 people draw guns. Which ones are the active shooter and who is not? And do you want to be the person holding a gun when the police arrive? 

Or in the case we started with -- Ahmaud Arbery -- we have gun armed people "arresting" a jogger. How can the jogger (who was innocent of any crimes so far as we can tell) determine that these are "well intentioned" citizens making a mistaken arrest and not criminals out to rob him?

This goes to a major flaw in self defense with guns -- you can create a chain of self defense claims from one misunderstanding where a bunch of people are dead and yet there is no crime. Does this not suggest some need for introspection on gun use in public places? Now, to be clear, public places is very important. I have thoughts about private spaces, as well, but they are way less clear. If Ahmaud Arbery had been on private property and not a public street then many of the issues would have been different in important ways. There are also issues with retreating when you might be responsible for young children and the aggressor is moving quickly. These are not the cases we are thinking about. 

Instead, it is the way that you can be provocative in a public space and then be completely covered by self defense for the confrontation that you provoked. And there is no way that Ahmaud Arbery wasn't aggressively confronted before the shooting, there is even video of the encounter. But as soon as you think about citizen's arrests for actions in the past (see first tweet) in cases of dubious identification, it quickly becomes clear that this could be used by bad actors in a variety of ways.