The Islamic Center of Columbia, Tennessee—a small city about 45 miles south of Nashville—had been around for only a few years when white supremacists burned it down. On a Saturday in early 2008, three young men went to the mosque armed with spray paint and Molotov cocktails. According to a federal indictment, they first defaced the exterior walls with swastikas and phrases including White Power. Then they broke into the building and set it aflame. “Everything on the inside was charred,” a former member of the Islamic Center told me. “The roof had come down, and they had to demolish...