It doesn't matter how untrue a thing is. If enough people (especially people we look up to) repeat it often enough, it soon becomes conventional wisdom.
A hundred years ago, Gustave Le Bon understood this when he wrote his classic work on crowds. He realized that the popular mind wanted most of all to simplify things.
Le Bon called the process - by which an idea gets simplified, repeated, imitated, and spread by the crowd - contagion.
~ Bill Bonner and Lila Rajiva, Mobs, Messiahs, and Markets (2007)