President Obama on Wednesday will visit a U.S. mosque for the first time in his presidency. According to the White House, during this visit he will “celebrate the contributions Muslim Americans make to our nation and reaffirm the importance of religious freedom to our way of life.” Over the past two years, in the president’s efforts to counter violent extremism, he has emphasized the responsibility of Muslim “scholars and clerics” to help ensure that mosques are not used as a platform to preach Islamist extremism.

Such extremism...