At a recent showing of “A Complete Unknown,” the new Bob Dylan biopic, a cheerful group of young women settled in to watch the delicately handsome Timothée Chalamet impersonate the singer.

They barely noticed the 80-year-old man sitting next to them, armored in a winter coat and hat that he never removed. Then, the film began.

“This is all made up,” the man brayed at the screen.

“It’s not what you think it is.”

“You’re scum!”

And so A.J. Weberman’s full-throated annotation of the film continued for 2 hours and 20 minutes, replete with dark interpretations of lyrics and references to how Dylan and the film intersected with such things as communism, the Bay of Pigs Invasion, the C.I.A. and Barry Goldwater.

The group of women exchanged confused glances, but said nothing.

For more than half a century, the lives of Weberman and Dylan have been intertwined — though it is Weberman who has done most of the intertwining.

He began as one of Dylan’s keenest observers and fans, so intent on digging into the singer’s life that he sifted through trash cans outside 94 MacDougal Street, where the singer once lived. But he became Dylan’s nemesis, calling him a hoaxer and sellout, attacking him with an obsession bordering on madness.

Now that Dylan is getting a Hollywood moment, Weberman sees a renewed opportunity to advance the anti-Dylan agenda that has sustained him for decades. He is writing a new book interpreting Dylan’s lyrics, and answering a cascade of emails and calls asking for his take on the film.