this is where the mythological concept of sin sorta helps. So its a bad thing but basically you decide at what point doing the bad thing is worse than other bad things but you can't ever make it not a bad thing. You just accept its price at some point and its ultimately and individual decision and I don't think many will know until that moment. For myself I try to avoid it as much as I can but I don't know in what situation I will be driven to it.
It's always a matter of degrees. The bigger the injustice, the more violence is justified to rectify it. It is in the disproportionality, in my view, where the problem arises.
Never forget that humans are just barely evolved apes. Sometimes a swift knock to the head is required to activate those neural pathways to discourage anti-social behavior. Not always, but also not never. Claiming otherwise is just self-aggrandizing moralization that people use to make themselves sound and feel superior.