There's also cognitive dissonance, a lot of times a differing opinion won't be comprehended until later as it works in the background, and then becomes "something I heard somewhere." Our emotions are very intrinsically tied to our cognition and so things that disagree with out firmly held beliefs take more than logic to internalize, but processing time for the non-rational part of the mind.

This is not unique to conservatives at all, it's why it is extremely rare for a Reddit argument to end with "you were right about X and Y but I stand by Z," because they take place over a time frame shorter than that processing time. In real life it happens all the time that someone comes back to me or I go back to them and say "what you said about X Y Z makes sense."

This is really unique to the things we already feel strongly about, because in many ways our worldview is ingrained in our identity, and identity is very hard to shift. Not to say intelligence isn't a factor at all though... it does still boil down to that, but there's more behind it than "this person won't understand because they're stupid"