On September 11, 2001, al-Qaeda operatives slaughtered nearly 3,000 Americans in an operation that marked the second major attack by violent jihadists against the World Trade Center. There wasn’t much mystery about who had carried out these atrocities — unless you were Salam al-Marayati, executive director of the Muslim Public Affairs Council. Marayati warned Americans not to conclude that the suicide hijacking attacks were the work of Muslim terrorists. “If we are going to look at suspects,” he told a Los Angeles radio station, “we should look at groups that benefit the most from these kinds of incidents, and I...