Then of course there's Nelson Mandela. He started with peaceful means, came to the conclusion it was ineffective in his case and turned to violence. Later he refused opportunities to leave prison that would have required him to renounce violence. Ultimately, he didn't need to fire a shot after he was released but he would have done so with a clear conscience. Non-violence can be a moral choice, but so can violence in the face of great, violent injustice.

Of course, we're assuming asymmetric warfare here. No-one honestly believes FDR was wrong to declare war on Japan.