so what you're saying is the killing of others is violent if you can somehow justify it...
that's a weird definition of violence.
According to the dictionary definition of violence:
: exertion of physical force so as to injure or abuse (as in warfare effecting illegal entry into a house) b : an instance of violent treatment or procedure
2 : injury by or as if by distortion, infringement, or profanation : outrage
3 a : intense, turbulent, or furious and often destructive action or force b : vehement feeling or expression : fervor; also : an instance of such action or feeling c : a clashing or jarring quality : discordance
4 : undue alteration (as of wording or sense in editing a text)
killing Nazis would be considered violent, no matter what (unless we use your non-dictionary definition, of course).
Well, let's say there's this guy (for the sake of this story, his name will be Hidler). And he hates a race of people (The Joos) and he decides to kill them all in a holocaust (about six million).
We stop him with violence (War is pretty violent, right?). I would say saving all the Joos from Hidler through violent means is justified.