Shehzad Tanweer was the bright, Muslim son of a first-generation Pakistani immigrant into Britain. His father owned a fish-and-chips shop, and Shehzad, at 22, was a university student headed for a profession--the kind of story of immigrant assimilation that is so familiar in America. Instead, Tanweer became a murderer, killing himself and other fellow travelers in the morning rush hour on London's Underground.Muhammad Bouyeri, born in the Netherlands, shot Theo Van Gogh, a Dutch filmmaker and a descendant of the painter, six times while Van Gogh was bicycling in Amsterdam. Then he cut Van Gogh's throat and, with his knife,...