I have massive problems with the "social" "sciences," especially "psychology." But it thought it would be fun to see what Psychology Today had to say about this very very good question.

A Fragile Ego Leads to Attempts to Distort Reality

Some people have such a fragile ego, such brittle self-esteem, such a weak "psychological constitution," that admitting they made a mistake or that they were wrong is fundamentally too threatening for their egos to tolerate. Accepting they were wrong, absorbing that reality, would be so psychologically shattering that their defense mechanisms do something remarkable to avoid doing so—they literally distort their perception of reality to make it (reality) less threatening. Their defense mechanisms protect their fragile ego by changing the very facts in their mind, so they are no longer wrong or culpable.

Another place I thought of to look--Ted Kaczynski's "manifesto," in which he traced out the liberal/left mindset so well. E.g.:

“It is obvious that [leftists] are not cool-headed logicians systematically analyzing the foundations of knowledge. They are deeply involved emotionally in their attack on truth and reality.”

Also:

The leftist’s feelings of inferiority run so deep that he cannot tolerate any classification of some things as successful or superior and other things as failed or inferior. This also underlies the rejection by many leftists of the concept of mental illness and of the utility of IQ tests. Leftists are antagonistic to genetic explanations of human abilities or behavior because such explanations tend to make some persons appear superior or inferior to others. Leftists prefer to give society the credit or blame for an individual’s ability or lack of it.

And finally:

Leftists may claim that their activism is motivated by compassion or by moral principles, and moral principle does play a role for the leftist of the oversocialized type. But compassion and moral principle cannot be the main motives for leftist activism. Hostility is too prominent a component of leftist behavior; so is the drive for power. Moreover, much leftist behavior is not rationally calculated to be of benefit to the people whom the leftists claim to be trying to help. For example, if one believes that affirmative action is good for black people, does it make sense to demand affirmative action in hostile or dogmatic terms? Obviously it would be more productive to take a diplomatic and conciliatory approach that would make at least verbal and symbolic concessions to white people who think that affirmative action discriminates against them. But leftist activists do not take such an approach because it would not satisfy their emotional needs. Helping black people is not their real goal. Instead, race problems serve as an excuse for them to express their own hostility and frustrated need for power.