Give people who either love violence, or don't mind someone else using it to protect them, a rhetorical inch and they will take a real mile. If Gandhi were around today, he'd be dashing about trying to answer all those who excuse violence with the smug assurance that even Gandhi would have approved, as is evident by his regrettable line, "I do believe that where there is only a choice between cowardice and violence I would advise violence."
This was in the aftermath of the Jallianwala Bagh Massacre of hundreds of innocent civilians, perhaps more than 1,500, at the command of Reginald Dyer, the British officer who will go down in history as a criminal against humankind. That massacre was simply the worst act of direct terrorism committed by the British empire upon the restive India, but it came in the context of other violence and in the immediate aftermath of the passage of the draconian Rowlatt Acts, curtailing civil rights for Indians in India after some 1.3 million Indians had aided the British as they fought World War I, either as soldiers or in logistical support. It was also just as Gandhi was emerging as a leader in India, and many assumed his nonviolence was a cover for his plans to later use military insurgency. His Doctrine of the Sword was written in that context and all it was meant to do was to reassure everyone that he had no secrets, that he was openly honest in his choice of nonviolence. Indeed, he ended that piece of writing:
--Young India, Ahmedabad, Wednesday, 11th August, 1920.
In other words, he was telling those who hoped he had a violent plan after using nonviolence to gain some following that they should not use violence thinking that he secretly wanted it. Sadly, the earlier unfortunate sentence is repeated ad nauseam by those who don't mind misquoting Gandhi by lifting out a bit that he later explains quite well.
But this is how it usually is. Those who want to use violence can quote the Bible, the Qur'an, Augustine or Aquinas, and even Gandhi. Justifying violence is child's play, because so many want to believe it works in their favor. Show me a violent attack and I'll construct an argument based on these sources. Easy beans, violence is permitted, q.e.d. But most of those violent attacks were not done in the spirit of the 'proof' and none of them likely lacked alternative paths to management, if not resolution.
More than 1 million Afghan, Iraqi, US, British, Canadian, Pakistani, and other human lives, huge mountains of irreplacable natural resources and in excess of $1.1T from the US treasury so far--that is the cost of war since 9.11.01. Can we look at that cost and honestly say we had no logical alternatives?