Many people...far too many...see this world in black and white. For them, every human idea, trait or point of view is either right or wrong, good or bad, divine or evil; there is no room for dissent, discussion or compromise.
This rigid approach to life is usually ingrained in childhood and reinforced by a cloistered youth, with exposure to a limited circle of relatives and friends. Those who continue to live in such confinement, not motivated to explore the "outside world" via education or travel, tend to retain their simplistic and dogmatic views. In turn, these provincial attitudes foment intolerance, often surfacing as racism, religious zealotry and other forms of discrimination.
Intolerance of other ideas and points of view, a product of early, self-righteous reinforcement by parents or mentors, hinders one's ability to function effectively in relationships and in human society as a whole. Faced with this reality, unwilling to compromise and incapable of trusting "outsiders," such people seek the comfort of like-mined individuals; in this way, intolerance feeds on itself, fringe groups form and the welfare of human society is placed at risk. It is only through education and personal experience, free from religious and political constraints, that we come to appreciate the shades of gray in our lives.