Iranians have adopted a new sport in the past few years: knocking the turban from a passing cleric’s head. There are points for technique and for how high and how far you can get their headgear to go. These are small acts of revenge against a hated religious elite who came to power on a wave of arrests and torture and who, as recently as January, ordered thousands of peaceful protesters to be shot in the streets. It’s also a symptom of something larger. Political Islam is in retreat across the Middle East and the wider Muslim world. “The strange...