It's called an echo chamber. Hitler and the Nazis employed a similar tactic in that whether it was fact or fiction, if it's repeated enough, it becomes fact to the general public.
It's unfortunate for the rest of us who are either right or other. Long ago they silenced their detractors in the media, now they are killing them at the town halls. They don't support free speech, freedom of thought, questioning of the status quo.
They've made Trump the boogey man to further escalate their end goal of violence and destruction of 70% of the American populace.