Assalamu alaikum
Some people shall always see something they want to see, regardless of whether it is actually there or not.
Allah has made mention of these people in the Quran, in the following words: The parable of those who reject Faith is as if one were to shout Like a goat-herd, to things that listen to nothing but calls and cries: Deaf, dumb, and blind, they are void of wisdom.(2:171)
I think pride is another contributing factor. Instead of people giving in, even though they know they are wrong within themselves, pride claws away at people and doesn't allow many to admit defeat.
Brainwashing-- You have something drummed into you for a long period of time and you are more likely to swallow it accepting it to be correct instead of questioning it.
Ma'assalama