The new Muslim mayor of London has issued a warning to Donald Trump: Moderate your stance on Muslims, or they will launch more attacks against America. Trump recently praised Sadiq Khan for winning London’s mayoral race, and said he would be willing to create an exception in his policy restricting Muslim entry into the United States in order to allow Khan to visit. But in a statement Tuesday, Khan dismissed Trump’s invitation, and also denounced his views on Islam as “ignorant,” suggesting Trump’s policies would increase the terrorist threat in both the U.S. and U.K. “Donald Trump’s ignorant view of...