The amount of suffering and pain caused by the tyranny of human beings over other animals (particularly in food production) far exceeds that caused by sexism, racism, or any other existing form of discrimination, and for this reason, the animal liberation movement is the most important liberation movement on the face of the planet today.
(p. 278) - Darwin, God and the Meaning of Life: How Evolutionary Theory Undermines Everything You Think You Know (2010)