As the Yazidis are seeing, when the group that is killing them is killing them for their very existence (because they believe in a different god you see), non violence is not exactly helping them. If anything, fighting and fighters are. Candlelight vigils, peace marches and sit ins and demonstrations are not exactly furthering their cause.
Ask the other minority communities in the Middle east. The Parsis of Iran. The Pandits of Kashmir. The Hindus in Pakistan. And the Sikhs there. And others like the aborigines and American Indians and the Hindus on whom an entire mountain range is named as Hindukush (killer of Hindus). How come being non violent never got them anywhere except closer to death?
And therefore, should not Israel defend itself against Hamas whose stated goal to eliminate Jews or should it just allow itself to be attacked by rockets?
Yes, to those who think that world peace will be achieved by keeping quiet, it is time to revisit this quote - the price of liberty is eternal vigilance. (By somebody)