If you ask someone why they believe something, chances are they don’t have an argument. They might have a quick rebuttal or a cliché one-liner. But if you ask specific questions and keep digging, you’ll find out more often than not they believe it because everyone else believes it. Particularly everyone else by whom that person is surrounded in their daily life.
The influence of those around us is far more powerful than truth or logic. This is a positive thing when the crowd is headed in the right direction. When they are not, however, you must be ready to quickly and quietly slip out the back door.