Many people base their conclusions on popularity. Thee must be a god or my god is the right one, because so many people believe the way I do. That is why comparative religion studies are helpful in that their thoughts of their beliefs being exclusive to a righteous group, can be challenged. It's a process that can result in questioning and exploration, but it also can end in ignoring the information and relying on cognitive dissonance.

I believe everyone has perception problems, meaning everyone sees things from their limited points of views due to their environment and understandings. To call people stupid because of this is stupid.

Like everything else there are varying degrees.

I have come across many that would fit that description during my lifetime, and unfortunately come to the conclusion that not only is it a waste of time to try and help, but that it is actually counter productive to try. You only end up making an enemy, rather to just leave well enough alone.