Since someone quoted Gandhi earlier, here are some more Gandhi quotes:

"He who cannot protect himself or his nearest and dearest or their honour by non-violently facing death may and ought to do so by violently dealing with the oppressor. He who can do neither of the two is a burden. He has no business to be the head of a family. He must either hide himself, or must rest content to live for ever in helplessness and be prepared to crawl like a worm at the bidding of a bully." – M.K. Gandhi, Between Cowardice and Violence

"I do believe that where there is only a choice between cowardice and violence I would advise violence." – M.K. Gandhi, The Doctrine of the Sword.

"When my eldest son asked me what he should have done, had he been present when I was almost fatally assaulted in 1908, whether he should have run away and seen me killed or whether he should have used his physical force which he could and wanted to use, and defended me, I told him that it was his duty to defend me even by using violence." – M.K. Gandhi, The Doctrine of the Sword.