Ditto Phizzy. When you're constantly taught that there is only one way of understanding something, it can be very hard to entertain another perspective. I think many trot out a default response without really noticing how distorted, illogical or even plain ridiculous it is. It's a blind spot.
To add: If they have an inkling that something doesn't make sense yet promote their default position to the death, that's just a self-defense/self-preservation mechanism to keep them from having a meltdown.