In the 1970s, Korean cult leader Sun Myung Moon coined a term for the attitude assumed by “Moonies”—members of his crackpot Christianity spin-off, the Unification Church. “What face could better represent love than a smiling face? This is why we talk about love bomb; Moonies have that kind of happy problem,” he said.

Beneath the attentive smile, however, lurked a sinister reality. After Moonies had identified a potential recruit, their love bombing—a technique of emotional manipulation in which a person is bombarded with flattering attention—began. One former recruit testified that he had only agreed to go along to his first meeting because he thought the women who suggested it were flirting with him. Two years later, he had become so deeply indoctrinated that his family hi...