The ayatollah's grandson calls for a U.S. invasion of Iran. I have no respect for the hereditary principle and neither does Shiite Islam, which considers earthly kingship to be profane. But no one can be completely uninterested in heredity per se, and my first thought, on meeting Hossein Khomeini, was that he has his grandfather's eyebrows. Still, our conversation quickly banished the notion that this 45-year-old cleric is the least bit interested in running for his grandpa's job. He is a relatively junior cleric—a sayeed—but he wears the turban and robe with some aplomb and was until recently a resident...