confirmation bias
The TL;DR is, we tend to stick with what we think, even though we know we're wrong about some things.
Everyone has confirmation bias. That's why it's important to recognize. It blinds us and others. It's the reason we can't agree on things that we think are so fundamental or obvious.
I'm certainly not perfect at it, but part of my ethos is critically analyzing things that I believe. I get why most people don't do this. This feels dangerous because, well, it is. It also takes effort. It means actually listening to the other side, questioning why we believe what we believe, considering things that we don't want to be true, and putting things that we do want to be true on the chopping block.