A large percentage of humans are gullible. Too many people believe what politicians say, and what the media tells them, unless they have been exposed as lying in the first place. No doubt most sheep who watch FOX news belong to the dumb, gullible, and ignorant club. I don't know if gullibility decreases with increasing intelligence, but I hope so.
Culture can be to blame as well. Too many people are indoctrinated to believe that fat people are unhealthy, and that the majority of muslims are "terrorists".... a vague and broad term that. And some can't even pinpoint other countries on a world map.
Also, did you know that the word 'gullible' has been removed from the Oxford dictionary?
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Lalalalai.... I'll cut you up!