I would concede that point as causing part of the problem, but not all of it. L. Brent Bozell and National Review and company have been on this issue since around 1964 when they found out how the mainstream media was treating Goldwater, so this crying foul goes way back before Hannity and company. As a matter of fact, Brent Bozell Jr. was the conservative personality who ran the main conservative media watchdog outfit in the '90s that persistently pointed out liberal bias in the news. But despite the obvious insularity of this arrangement, people had left the mainstream news long ago for this very reason. Study after study confirms at least a leftward tilt in the news, especially in the arbiters of what is newsworthy -- the journalists' leanings themselves, and in addition to that, the journalists' stated goals of their journalism. Right-of-center people don't need people to tell them to distrust the media. They just experience their worldview as radically different than the narrative that drives the news.
But that said, there's an element of media distrust being an insular and self-perpetuating thing, especially in the hands of someone like Hannity, or before that, the NR men. And when the alternative to a leftist narrative is conspiracy theories and alternative facts, that gets really, really worrisome. You wind up with people rioting or committing insurrection at the Capitol that way, and I think everyone here agrees that that is a universal bad.