Some things are believed because they are demonstrably true, but many other things are believed simply because they have been asserted repeatedly and repetition has been accepted as a substitute for evidence.
The press has made up so much...God...awful, horrifying stories...it has made me realize the more often you hear a lie, I mean, you begin to believe it.
Any stupid remark, quoted often enough, becomes gospel.
'America has no culture!' is a phrase that we've all heard many times in our lives. As is often the case, a lie repeated often enough becomes an assumed truth (kind of like the tall tale of Janeane Garofalo being a comedian).
One comes to believe whatever one repeats to oneself sufficiently often, whether the statement be true or false.
Man is so made that if he is told often enough that he is a fool he believes it.