“Violence is never the answer but sometimes, like with cockroaches, it is the only possible response.”

Violence is the Only Way http://www.nytimes.com/1988/01/03/books/violence-is-the-only-way.html?pagewanted=1

Source: An Ideal Husband

Source: Eat, Pray, Love

Source: Warlock

Interview for KFRC RKO Radio (8 December 1980)

Byrne, Robert. The 2,548 Wittiest Things Anybody Ever Said, page 372. http://books.google.com/books?id=odz2rZirMAkC&pg=PT372 Simon and Schuster, 2012. ISBN 145164891X
Attributed

Surreal
Lyrics, Duty

Interview on The David Frost Show (14 June 1969)
Context: We're trying to sell peace, like a product, you know, and sell it like people sell soap or soft drinks. And it's the only way to get people aware that peace is possible, and it isn't just inevitable to have violence. Not just war — all forms of violence. People just accept it and think 'Oh, they did it, or Harold Wilson did it, or Nixon did it,' they're always scapegoating people. And it isn't Nixon's fault. We're all responsible for everything that goes on, you know, we're all responsible for Biafra and Hitler and everything. So we're just saying "SELL PEACE" — anybody interested in peace just stick it in the window. It's simple but it lets somebody else know that you want peace too, because you feel alone if you're the only one thinking 'wouldn't it be nice if there was peace and nobody was getting killed.' So advertise yourself that you're for peace if you believe in it.

At the White House Summit on Countering Violent Extremism http://www.usatoday.com/story/news/nation/2015/02/18/obama-white-house-summit-on-countering-violent-extremism-speech/23631625/ (18 February 2015)
2015