When you teach a man to hate and fear his brother, when you teach that he is a lesser man because of his color or his beliefs or the policies he pursues, when you teach that those who differ from you threaten your freedom or your job or your family, then you also learn to confront others not as fellow citizens but as enemies, to be met not with cooperation but with conquest; to be subjugated and mastered. We learn, at the last, to look at our brothers as aliens, men with whom we share a city, but not a community; men bound to us in common dwelling, but not in common effort. We learn to share only a common fear, only a common desire to retreat from each other, only a common impulse to meet disagreement with force.