All murders happen because of emotional (killing someone in anger), economical (Theft gone wrong) or psychological (Doesn't realize it's wrong) reasons. none of these is prevented by sticking the murderer in a box after the murder.

All of these are prevented by building strong social network to manage any harmful impulses before something happens, which is something any reasonable anarchist would agree with.

Also If you think the list is incomplete then feel free to give another example.

Oh yeah also political assassinations and wars. But your comment already addresses those.

I think a better wording is that anarchy is naive. And I'd rather be naive than accept that this is the best we can come up with, because that's depressing.