It's worse than that, actually. They may be idiotic, but not much more than anybody else. They are fairly ordinary people whose worldview currently depends on the idea that Donald Trump is a good guy, maybe flawed, but nevertheless good, and that worldview is obviously threatened. And now they are presented with facts about him they don't like:
Have you ever noticed that when you present people with facts that are contrary to their deepest held beliefs they always change their minds? Me neither. In fact, people seem to double down on their beliefs in the teeth of overwhelming evidence against them. The reason is related to the worldview perceived to be under threat by the conflicting data.
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proponents' deepest held worldviews were perceived to be threatened by skeptics, making facts the enemy to be slayed. This power of belief over evidence is the result of two factors: cognitive dissonance and the backfire effect.
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In a series of experiments by Dartmouth College professor Brendan Nyhan and University of Exeter professor Jason Reifler, the researchers identify a related factor they call the backfire effect “in which corrections actually increase misperceptions among the group in question.” Why? “Because it threatens their worldview or self-concept.”
http://www.internationalskeptics.com/forums/showthread.php?postid=14090734#post14090734