We're built to play games. Until we hit the formal operational stage (at puberty), we basically have a bunch of individual, contextual constraint solvers operating mostly independently in our minds, one for each "game" we understand how to play—these can be real games, or things like status interactions or hunting. Basically, each one is a separately-trained decision-theoretical agent.

The formal operational psychological stage signals a shift where these agents become unified under a single, more general constraint-solving mechanism. We begin to see the meta-rules that apply across all games: things like mathematical laws, logical principles, etc. This generalized solver is expensive to build, and expensive to run (minds are almost never inside it if they can help it, rather staying inside the constraint-solving modes relevant to particular games), but rewards use, as anyone here can attest.

When we are operating using this general solver, and we process an assertion that would suggest that we must restructure the general solver itself, we react in two ways:

Initially, we dread the idea. This is a shade of the same feeling you'd get if your significant other said, very much out of the blue and in very much the sort of tone associated with such things, "we need to talk." Your brain is negatively reinforcing, all at once, all the pathways that led you here, way back as far as it remembers the causal chain proceeding. Your mind reels, thinking "oh crap, I should have studied [1 day ago], I shouldn't have gone out partying [1 week ago], I should have asked friends to form a study group [at the beginning of the semester], I never should have come to this school in the first place... why did I choose this damn major?"

Second, we alienate ourselves from the source of the assertion. We don't want to restructure; not only is it expensive, but our general solver was created as a product of the purified intersection of all experiments that led to success in all played games. That is to say, it is, without exception, the set of the most well-trusted algorithms and highly-useful abstractions in your brain. It's basically read-only. So, like an animal lashing out when something tries to touch its wounds, our minds lash out to stop the assertion from pressing too hard against something that would be both expensive and fruitless to re-evaluate. We turn down the level of identification/trust we have with whoever or whatever made the assertion, until they no longer need to be taken seriously. Serious breaches can cause us to think of the speaker as having a completely alien mental process—this is what some people say of the experience of speaking with sociopathic serial killers, for example.

Of course, the mind can only implement the second "barrier" step when the assertion is associated with something that can vary on trust, like a person or a TV program. If it comes directly as evidence from the environment, only the first reaction remains, and intensifies increasingly as you internalize the idea that you may just have to sit down and throw out your mind.