“[Their foremost task] … is to denounce the violence on which the present system is based, and all the evil — material and spiritual — this entails for the masses of menu throughout the world…. So long as we are not dealing honestly and adequately with this ninety percent of our problem, there is something ludicrous, and perhaps hypocritical, about our concern over the ten percent of violence employed by the rebels against oppression.”

Source: Attributed from posthumous publications, Dialogues of Alfred North Whitehead (1954), Ch. 29, June 10, 1943.
Context: Ninety percent of our lives is governed by emotion. Our brains merely register and act upon what is telegraphed to them by our bodily experience. Intellect is to emotion as our clothes are to our bodies; we could not very well have civilized life without clothes, but we would be in a poor way if we had only clothes without bodies.

Source: Attributed in posthumous publications, Einstein and the Poet (1983), p. 31
Spoken on hearing German marchers singing war songs. On p. 474 of Alice Calaprice's The Ultimate Quotable Einstein, she lists "we only use 10 percent of our brain" as a quote "misattributed to Einstein", perhaps this is the source of the misquote? Einstein seems to be speaking metaphorically here, not endorsing the myth http://www.snopes.com/science/stats/10percent.asp that science has shown 90 percent of the neurons in our brain lie dormant. And the myth dates back to before this interview, for example the book Mind Myths: Exploring Popular Assumptions About the Mind and Brain, edited by Sergio Della Salla, has a chapter by Barry L. Beyerstein titled "Whence Cometh the Myth that We Only Use 10% of our Brains?" which shows on p. 11 an advertisement from the 1929 World Almanac containing the line "There is NO LIMIT to what the human brain can accomplish. Scientists and psychologists tell us we use only about TEN PER CENT of our brain power."
Context: What a betrayal of man's dignity. He uses the highest gift, his mind, only ten percent, and his emotions and instincts ninety percent.

Peter Gelderloos, How Nonviolence Protects the State http://theanarchistlibrary.org/library/peter-gelderloos-how-nonviolence-protects-the-state (Cambridge, MA: South End Press, 2007), 37.

Fighting the Lamb's War: Skirmishes with the American Empire (1996), p. 217
Context: According to a University of South Carolina study, violence in America rose 42 percent during the Vietnam War. This is hardly surprising. Our leaders are lawless, so why not we? If the government threatens other countries with the bomb, why not threaten one another with handguns? If our leaders are raping the planet, why not our neighbors? Our leaders create a climate of fear and violence. Why do they appear shocked when Americans kill, rob, and maim one another?

1941 - 1967
Source: a letter to Margaret McKellar, 14 November 1965; as quoted in Edward Hopper, Gail Levin, Bonfini Press, Switzerland 1984

1950s, Three Ways of Meeting Oppression (1958)
Context: A second way that oppressed people sometimes deal with oppression is to resort to physical violence and corroding hatred. Violence often brings about momentary results. Nations have frequently won their independence in battle. But in spite of temporary victories, violence never brings permanent peace. It solves no social problem; it merely creates new and more complicated ones.

Ron English's Fauxlosophy: Volume 2 (2022)

Speaking at a meeting of the American Economic Association, as quoted by Walter Block in "Milton Friedman RIP" in Mises Daily (16 November 2006) http://mises.org/story/2393

Letter to William J. Kennedy (12 July 1967), p. 630
1990s, The Proud Highway : The Fear and Loathing Letters Volume I (1997)