To make matters worse, socially-defined beliefs add tremendous bias. Whereas most people stop believing in Santa, the Tooth Fairy, etc., because of implausability or lack of evidence, peer expectations can override that doubt.
Religious doctrine is an example. No one believes it physically possible that Noah could have made an ark that big, or crammed two of every species on the boat, but that doesn't prevent many people from believing that the story is true.
Ironically, people use knowledge of this susceptibility to irrational belief to support their own irrational belief systems (i.e. "Anthropogenic global warming is a mass delusion"), because their own belief is that an opposing group is irrational. Even more ironically, they are correct because the other group has an irrational majority. Most people do not believe that anthropogenic global warming is real because of the evidence, but because their peers have convinced them so.
Just because someone is correct, it doesn't mean that they arrived at their conclusion rationally. Also, just because someone has a socially-defined belief, it doesn't mean they are incorrect.