“Humans can never escape personal motives and prejudices. It's in our nature.”
Related quotes
“Prejudice locks the mind. Nothing can enter. Nothing true can escape.”
Source: How to Argue and Win Every Time (1995), Ch. 6 : The Power of Prejudice : Examining the Garment, Bleaching the Stain, p. 74

“…prejudice and the well-known weaknesses of human nature are to be exploited and thus encouraged.”
Source: Are We Victims of Propaganda, Our Invisible Masters: A Debate with Edward Bernays (1929), pp. 143-144
Source: How to Argue and Win Every Time (1995), Ch. 6 : The Power of Prejudice : Examining the Garment, Bleaching the Stain, p. 74

Source: The Expanding Circle: Ethics, Evolution, and Moral Progress (1981), Chapter 6, A New Understanding Of Ethics, p. 172

A message to Eckermann on March 11, (1832), translated by Albert Schweizer in Goethe: Five Studies http://archive.is/tOo5z (1961), Beacon Press, p. 56