Violence must be organized and accountable to be just. Non-violence is always preferred, and is always the initial approach.
But if there is a credible threat, defensive violence is OK as long as whoever is being violent accepts whatever accountability may come.
I'm conflicted about it, but the fact is one reason the US has been so successful in leading the world in relative peace (as compared to WWII and before, not compared to the ideal) is because we have so much capacity for violence in our back pocket.
"Talk softly and carry a big stick."