She recalled how people were stigmatized in the early years of the AIDS epidemic and the way that stigmas become the focus of attention and get in the way of the efforts really needed to avert tragedy.

Mr. King’s contention that Muslims are not cooperating with law enforcement is just wrong. According to the Triangle Center on Terrorism and Homeland Security, an independent research group affiliated with Duke University and the University of North Carolina, 48 of the 120 Muslims suspected of plotting terror attacks in the U.S. since Sept. 11, 2001, were turned in by fellow Muslims. In some cases, they were turned in by parents or other relatives.

What are we doing? Do we want to demonize innocent people and trample on America’s precious freedom of religion? Or do we want to stop terrorism? There is no real rhyme or reason to Congressman King’s incoherent flailing after Muslims. Witch hunts, after all, are about seeing what kind of ugliness might fortuitously turn up.

Mr. King was able to concoct the anti-Muslim ugliness in his 2004 novel, “Vale of Tears,” in which New York is hit yet again by terrorists and, surprise, the hero of the piece is a congressman from Long Island. But this is real life, and the congressman’s fantasies should not apply.

America should be better than this. We’ve had all the requisite lessons: Joe McCarthy, the House Un-American Activities Committee, the demonization of blacks and Jews, the internment of Japanese-Americans, and on and on and on. It’s such a tired and ugly refrain.

When I asked Colleen Kelly why she spoke up, she said it was because of her great love for her country. “I love being an American, and I really try to be thankful for all the gifts that come with that,” she said. But with gifts and privileges come responsibilities. The planned hearings into the Muslim community struck Ms. Kelly as something too far outside “the basic principles that I knew and felt to be important to me as a citizen of this country.”