MARTINSBURG, W.VA. — Caleb Cain pulled a Glock pistol from his waistband, took out the magazine and casually tossed both onto the kitchen counter.
“I bought it the day after I got death threats,” he said.
The threats, Mr. Cain explained, came from right-wing trolls in response to a video he had posted on YouTube a few days earlier. In the video, he told the story of how, as a liberal college dropout struggling to find his place in the world, he had gotten sucked into a vortex of far-right politics on YouTube.
“I fell down the alt-right rabbit hole,” he said in the video.
Mr. Cain, 26, recently swore off the alt-right nearly five years after discovering it, and has become a vocal critic of the movement. He is scarred by his experience of being radicalized by what he calls a “decentralized cult” of far-right YouTube personalities, who convinced him that Western civilization was under threat from Muslim immigrants and cultural Marxists, that innate I.Q. differences explained racial disparities, and that feminism was a dangerous ideology.
“I just kept falling deeper and deeper into this, and it appealed to me because it made me feel a sense of belonging,” he said. “I was brainwashed.”
Some young men discover far-right videos by accident, while others seek them out. Some travel all the way to neo-Nazism, while others stop at milder forms of bigotry.
The common thread in many of these stories is YouTube and its recommendation algorithm, the software that determines which videos appear on users’ home pages and inside the “Up Next” sidebar next to a video that is playing. The algorithm is responsible for more than 70 percent of all time spent on the site.
The radicalization of young men is driven by a complex stew of emotional, economic and political elements, many having nothing to do with social media. But critics and independent researchers say YouTube has inadvertently created a dangerous on-ramp to extremism by combining two things: a business model that rewards provocative videos with exposure and advertising dollars, and an algorithm that guides users down personalized paths meant to keep them glued to their screens.
“There’s a spectrum on YouTube between the calm section — the Walter Cronkite, Carl Sagan part — and Crazytown, where the extreme stuff is,” said Tristan Harris, a former design ethicist at Google, YouTube’s parent company. “If I’m YouTube and I want you to watch more, I’m always going to steer you toward Crazytown.”