Five days before the attack, Mr. Fillion invoked the threat of Muslim extremists, suggesting on his show that some wanted to “integrate and to live like us, and to get close to us, and, at an opportune moment, to hit us.” The Press Council of Quebec, a watchdog organization, upheld a complaint that found that the segment was “discriminatory” because it suggested that all terrorists were Muslims.

Mr. Fillion’s supporters said he had been taken out of context. (During Mr. Bisonnette’s trial, there was no evidence presented suggesting he listened to talk radio or to Mr. Fillion.) Mr. Fillion said he had been horrified by the mosque shooting, welcomed immigration and was not Islamophobic.

But talk radio has displayed an undercurrent of Islamophobia. The veteran radio host André “King” Arthur, poured scorn on Azzedine Soufiane, one of the mosque shooting victims, who had heroically lunged at Mr. Bissonnette. Mr. Arthur decided to highlight that Mr. Soufiane’s grocery store had received a $3,208 fine for food storage and cleanliness violations.

In a rare mea culpa after the mosque attack, Sylvain Bouchard, another prominent Quebec City talk radio host, reproached himself for failing to reach out to Muslims.

“We talk of Islam, we denounce radical Islam. But do we talk to them?” he asked.

The talk radio hosts have also been criticized for their treatment of women. On his show last year, Mr. Fillion suggested that some women sexually harassed by Harvey Weinstein were complicit in succumbing to his sexual caprices because they had “no values.”

Mr. Fillion said his main concern was that the “Me Too” movement was conducting “trials by social media.” He stressed he had two daughters.

“I’m zero misogynist,” he said. “Ask my wife.”

But Dominique Payette, a communications professor at Université Laval who wrote a report on talk radio in Quebec City, said Mr. Fillion and his fellow hosts were “dangerous.” She said they chased ratings by systematically targeting, among others, gays, welfare recipients, intellectuals and handicapped people.