In his presentation, Wakefield sounded impatient but righteous. He used enough scientific terms — “ataxic,” “histopathological review” and “vaccine excipients” — that those parents who did not feel cowed might have been flattered by his assumption of their scientific fluency. He also tried to defend himself against a few of the charges laid out in The British Medical Journal — offering defenses that did not hold up before the journal’s panel of editors but were perhaps enough to assure an audience of his fans that he did, in fact, have defenses. Some part of Wakefield’s cult status is surely because of his personal charisma, and he spoke with great rhetorical flair. He took off his glasses and put them back on like a gifted actor maximizing a prop. “What happens to me doesn’t matter,” he said at one point. “What happens to these children does matter.”

After the talk, a line of visitors snaked down the length of the lobby, his followers waiting to have Wakefield sign a book he wrote about his experience and convictions, “Callous Disregard.” “All right, love?” he said, handing the book back to one mother. “Of course,” he said when asked for a photo. A pregnant woman in the lobby told me she was there trying to educate herself. Another woman, with tears in her eyes, blamed herself for not working harder to obtain a separate measles vaccine for her possibly autistic child.

Michelle Guppy, the coordinator of the Houston Autism Disability Network and the organizer of the Tomball event, said she believed her own autistic son benefited greatly from one aspect of Wakefield’s work: his conviction that untreated gastrointestinal problems could be behind some of autism’s symptoms. It was Guppy, it turned out, who thought to hire the armed guards “to make the statement,” she said, “that this is neutral ground, and it’s going to be civil.” Guppy, a mother of two who was elegantly dressed for the occasion, made no pretense of neutrality herself. She narrowed her eyes when she learned that a writer from The New York Times was there to write about Wakefield.

“Be nice to him,” she said, “or we will hurt you.”