In response, Mr. Maza compiled a video of Mr. Crowder’s insults and tweeted them out, blaming YouTube for its inconsistent enforcement of its hate-speech policies. (One tweet read: “YouTube is dominated by alt-right monsters who use the platform to target their critics and make their lives miserable.”)

After an investigation, YouTube found that Mr. Crowder’s videos did not violate its rules. That set off an avalanche of criticism, and provoked backlash from L.G.B.T. groups and YouTube employees, who urged the company to do more to protect Mr. Maza and other creators from harassment. The controversy even ensnared Susan Wojcicki, YouTube’s chief executive, who was forced to apologize. Late last year, the site revised its harassment policy to address some of the concerns.

A YouTube spokeswoman declined to comment.

Inside the world of YouTube partisans, Mr. Maza’s feud with Mr. Crowder made him a scapegoat. Some creators blamed him for setting off an “adpocalypse” — a YouTube policy change that resulted in some videos being stripped of their ads. Others wove elaborate conspiracy theories that NBCUniversal, an investor in Vox, was using Mr. Maza to drive viewers and advertisers away from YouTube and toward its own TV platform.

In July, Vox ended Mr. Maza’s show, and after a few months in limbo, he decided to hang his own shingle. He set up a YouTube channel and a Patreon crowdfunding account, bought a camera and hit record. For all its flaws, he said, YouTube is essential for people who want to get a message out.

“The one thing that YouTube offers that’s really good is that it does give a space for independent journalists to do important work and build an audience without requiring a huge investment of capital,” Mr. Maza said.

YouTube can be harsh terrain for a professional leftist. The site is nominally open to all views, but in practice is dominated by a strain of reactionary politics that is marked by extreme skepticism of mainstream media, disdain for left-wing “social justice warriors” and a tunnel-vision fixation on political correctness.