In a slightly less specific vein (http://biphenyl.org/blog/2008/01/01/citation-needed/)...

I'm still waiting for this to happen at a real political rally.



…might also bear using on a sticker.

Putting a whole bunch of them on a t-shirt could work, too!

Hmm. I did go through a website full of logical fallacies looking for ones which could be snappily rendered into symbolic logic. I considered "correlation does not imply causation" but discarded it on the basis that I couldn't think of a snappy way to describe causation. I'm not entirely convinced by your answer; implication, after all, also does not imply causation. Smoke implies fire (yes yes, except where it doesn't), but smoke doesn't cause fire!