Debunking popular myths is often fraught with controversy, fallacy and futility, so before we do that, let's have fun with a myth that is not so popular nor controversial.
Athena punished Medusa by turning her hair tresses into snakes. Perseus then used Medusa's head as a weapon in battles.
Once upon a time, this story was popularly believed despite its obvious absurdity. In our modern times, other stories are widely believed, again, despite absurdity. A few of those follow.