It's not even belief, it's ambivalence. They've stopped learning. The critical thinking muscle atrophies and psycosclerosis (a hardening of the attitudes) ensues. I meet boomers (I'm of that vintage) all the time who have decidedly made up their minds based on misinformation from their past. Asking them to question these "beliefs" is goring their sacred cows. I no longer engage, there is no point. As for confirmation bias through their chosen media, the parroting has become my entertainment. When I hear the narrative repeated verbatim, I laugh, nod my head and excuse myself from the conversation.

Suffice it to say, I don't hang out with many folks my own age.