Apparently, a church dance in Greeley, Colo., led to 9/11. In 1948 Sayyid Qutb, an Egyptian writer who became the father of the radical Islamist movement, was sent to the United States to temper his contempt for the West. What he saw over two years — postwar consumerism, suburban lawns, men and women dancing “breast to breast” — only further inflamed his conviction that the West was the enemy of Islam and doomed. Mr. Qutb went on to work up a pseudospiritual justification of Islamic terrorism that inspired and emboldened many, including Osama bin Laden and his deputy, Ayman al-Zawahri....