Islam is quintessentially tolerant. Its adherents are hospitable to liberty, equality, and pluralism, the rudiments of modern democracy. Those committing terror in its name are heretics — a fringe which has “hijacked” a “religion of peace.” This conventional wisdom brims over the mainstream media’s daily servings. It is, moreover, the not-to-be-questioned premise of U.S. policy on a host of paramount issues: everything from how the war on terror is conceptualized and prosecuted, to the wisdom of negotiations with Iran, a sovereign state for Palestinians, agitation for freedom and popular self-determination throughout the Middle East, and the assumption that our own...