For almost as long as he can remember, Mathieu’s father had been a provocateur, with a penchant for inappropriate jokes and borderline remarks. But when he started dipping his toes into conspiracy theories, things quickly got out of hand. “When he told me to ‘look out for the FBI report’ proving Hillary Clinton tortured babies and drank their blood to live forever, I knew with 200 percent certainty that I had lost him,” Mathieu* recalled. “It was finished. I would never again see the person he was before.” As is often the case, the father’s cross over to “the other...