French: "Sir, (a+b^n)/n=x, therefore God exists: reply!" What Leonhard Euler said to Denis Diderot when he heard that Diderot was an atheist but not a mathematician. The funny part is that Diderot was so ashamed of his ignorance that he fled the country. One moral of this story is that, if you're going to be a decent atheist, you ought to be a decent mathematician.

See Catherine the Great, non sequitur, proof by intimidation.