The debate says 'never requires violence.' If I were in such a position where I am to deliver justice, I would most assuredly reatliate OR be the cause of the violence if I were of the belief that they were going to retaliate.

If ones attempts to use justice prove futile, then the next logical step is to use force and, if necessary, violence.

OR

If your efforts at justice are met with violence, then out of necessity you must use violence if only out of self-defence.

Personal opinion: I asked a relative if she would kill to save her son (she's a pacifist), her answer was precisely what is to be expected 'yes.'