In an interview, Mr. Sibrel said that his efforts to prove that men never walked on the Moon has cost him dearly. “I have suffered only persecution and financial loss,” he said. “I’ve lost visitation with my son. I’ve been expelled from churches. All because I believe the Moon landings are fraudulent.”

Ted Goertzel, a professor of sociology at Rutgers University who has studied conspiracy theorists, said “there’s a similar kind of logic behind all of these groups, I think.” For the most part, he explained, “They don’t undertake to prove that their view is true” so much as to “find flaws in what the other side is saying.” And so, he said, argument is a matter of accumulation instead of persuasion. “They feel if they’ve got more facts than the other side, that proves they’re right.”