Late last month, a young man named Kosoko Jackson became the second young adult author in five weeks to pull a debut work just before it hit the shelves . His book, “A Place for Wolves,” ran afoul of the sensibilities of the Twitter gatekeeping class, which deemed it insensitive to Muslims and unduly focused on people of privilege.

There was an obvious irony to his story, a karmic boomerang: Jackson, who is black and gay, often worked as a “sensitivity reader” for major publishing houses, which meant his job was to flag just the sort of problem content for which he was now being run out of town. He was Robespierre with his own neck in the cradle of the guillotine. One of the captains of “cancel culture” — which urges people to shun the insensitive, the oppressive, the morally questionable — got canceled himself.

As often happens with these things, the online pile-on was mainly led by people who hadn’t read Jackson’s book. It did start with someone who had — a reader who’d written an intemperate, if highly impassioned, review of an advance copy for the community website Goodreads. But it most likely would have remained just that, a pan from a citizen critic, had the review not been noticed by that corner of Twitter that’s obsessed with Y.A. fiction. Even by Twitter standards, it’s a hothouse subculture — self-conscious, emotional, quick to injure. Not unlike teenagers themselves.

I have read Jackson’s book. Before I get to the actual contents, let’s get this out of the way: What happened to Jackson is frightening. Purity tests are the tools of fanatics, and the quest for purity ultimately becomes indistinguishable from the quest for power. In the Twitterverse, ideologues have far more power than moderates. They have more followers; their tweets get more traction (studies have shown that emotional tweets pretty much always have more traction); they set the terms of their neighborhood’s culture and tone.