Believing that smart = right, thus, less smart = less right.
This is partly a product of the culture and it is part of why I turned down my scholarship and spent two decades as a homemaker. I was one of the top students at my high school and it was an incredibly poisonous experience.
Raising kids was a wonderful antidote to this shit. It helped me develop mental models concerning the superior density and value of local information, even in cases where a person has substantially less formal education.
In other words, my inarticulate 2 year old knew more about his situation than I did, never mind his lack of education and challenges in communicating it. Disrespecting his knowledge was guaranteed to go bad places. The challenge was in serving as an effective resource for him instead of simply trying to lord it over him.
They can be prone to thinking that if someone disagrees with them, the person is just stupid or doesn't know enough. It can be very challenging to get smart people from very different domains to collaborate effectively because both sides may throw their hands up quickly and assume the other side is just dumb.
Getting smart people with very different world views to really communicate in a meaty and respectful fashion can be challenging. Both sides may be quick to dismiss the other as both wrong and stupid.