MoreCooler.com: It's more cooler with the thing

Saw this somewhere..

"Never argue with a crazy person. You will just make him (or her) crazier, and a third person observing your argument may be unable to tell who is whom."

It's better than most pith, in that it's true rather than simply concise and cleverly worded. I've seen a couple examples of this one online recently (see Penny Arcade's argument with Squidi for examples).