If you resort to violent methods because the other side has destroyed your monastery, for example, you then have lost not only your monastery, but also your special Buddhist practices of detachment, love, and compassion.
I think there is a complicated side effect to overcoming evil in that we are forever changed by it. I think after we ingest some of the cruelty of the world, it takes years off of our lives, but it also gives us wisdom and a little grace, hopefully a sense of compassion.
When the only bond between close friends is attachment, then even a minor issue may cause one's projections to change. As soon as our projections change, the attachment disappears, because that attachment was based solely on projection and expectation. It is possible to have compassion without attachment, and similarly, to have anger without hatred.
Be guided, only by the healer of the sick, the raiser of the dead, the friend of all who were afflicted and forlorn, the patient Master who shed tears of compassion for our infirmities. We cannot but be right if we put all the rest away, and do everything in remembrance of Him. There is no vengeance and no infliction of suffering in His life, I am sure. There can be no confusion in following Him, and seeking for no other footsteps, I am certain!
'Thou shalt not kill' does not apply to murder of one's own kind only, but to all living beings and this commandment was inscribed in the human breast long before it was proclaimed from Sinai.
Peace must first be developed within an individual. And I believe that love, compassion, and altruism are the fundamental basis for peace. Once these qualities are developed within an individual, he or she is then able to create an atmosphere of peace and harmony. This atmosphere can be expanded and extended from the individual to his family, from the family to the community and eventually to the whole world.