More than a thousand Islamic extremists recently marched through the streets of Hamburg, Germany’s second-largest city, demanding that the European Union’s most populous and powerful country be reconstituted as an Islamic state governed by sharia. The demonstration, organized by a fast-growing Islamist group called Muslim Interaktiv, was allowed to proceed after left-wing parties in Hamburg’s legislature rejected a petition by right-wing parties to prohibit the event. During the April 27 march in Hamburg’s multicultural Sankt Georg district, the Islamists — mostly young men, but also women in chadors, hijabs, niqabs, and jilbabs — complained about an alleged surge in “Islamophobia”...