There is one difficulty in this debate: "Non-violence" is a tactical principle (as a moral or absolute principle it becomes a form of scabbing.) Hence one can debate it. But "Violence" is not a principle of any kind; it is an empty generalization, naming nothing specific. We don't have a word, it seems, to express a principle 'opposite' to Non-Violence. That causes considerable confusion, and I don't know how that confusion can be clarified.
Sometimes good results are achieved by killing people. The Paris Commune would not have lasted a day without willingness to kill.
Carrol