You have to meet the mediocre and the small minded on their turf. They can't rise to an ocassion.
I thought the adage went "Never argue with an idiot. They drag you down to their level and then beat you with experience."
Some people, when well-known sources tell them that fire will burn them, don't put their hands in the fire.
Some people, being skeptical, will put their hands in the fire, get burned, and learn not to put their hands in the fire.
And some people, believing that they know better than well-known sources, will claim it's a lie, put their hands in the fire, and continue to scream it's a lie even as their hands burn down to charred stumps.