@failures art,
I can never actually justify violence. There is no justification it of.
Back in the stone age when I was a Junior in high school, a teacher placed before us, as to killing and gun use. I was adamantly against. Ken asked (or was it his twin Bill?, no matter they were twerps), he asked if a gun was aimed at my mother would I shoot, I replied that I would not. He stared in disbelief (he did that all the time anyway), I explained it wasn't my place at for to intentionally end the life of another. Same stays true even now, as to my having that right. I am however at a time where I am aware that I can and will and even do react in ways I am against.
When pushed too far in a medical stay, I threatened a fellow patient. (Sorry, they called us "residents" (like that made the stay better?)). It wasn't justified, I knew better and guilt stays with me, even as his family said it needed to be did.
Fighting back, justifiable merely to a time making an escape but not with intended harm, push and shove and that is all. Killing, never justifiable. Even with that, there ate are a few that I'd want to destroy if they hurt threatened a person I care about, whether it might happen is a mystery. As of this writing, it is anger which brings me towards violence.