On July 8, Doug Williams, a 48-year-old assembly-line worker at the Lockheed Martin plant in Meridian, Mississippi, walked out of a meeting with managers on how to get along with fellow employees—just the sort of meeting encouraged by federal law to assure that everyone appreciates the merit of diversity and that no one is being harassed in the workplace. Minutes later, he returned with shotgun and a rifle. He shot two people in the room and three more on the factory floor. Then, he killed himself. Co-workers were not surprised. He had long threatened people. He had been to anger...