A coworker suggested a really terrific BBC podcast to me a while back called "In Our Time" (feed available here; the show also plays on NPR). It's a show that covers a lot of philosophically oriented topics, and this week's show was about alchemy.
One guy that was really into alchemy in his day was Newton, which I thought was interesting since when you think of Newton, you tend to associate him with the laws of motion and gravity and therefore some notion of rationality as well. But Newton was always a man who was concerned with the absence of spirituality in physics... a lot like Albert Einstein would be long after him.
This had me thinking about the old problem of science vs. religion.. both look for laws, but in different ways. The whole problem with religion, of course, is that the theories and laws are not testable, and therefore don't have a whole lot of logical value. To borrow an example from Carl Sagan, I could claim that there is an invisible, incorporeal pink dragon that lives in my apartment and demand that you feed it. Absurd? Prove me wrong. The fact that the notion is untestable makes it useless... whether it is "true" or not ceases to have any meaning.
There is a tendency among atheists (among whom I count myself) to become that which they despise because there is an elitist attitude that comes with the territory of being an intellectual minority: many become convinced on a fundamental level that there is no God, and that those who do believe in God are, by definition, rationally handicapped in some way.
I would argue that a fundamental disbelief in God is no better or worse than a fundamental faith in God. Newton and Einstein alone provide pretty compelling evidence that a belief in God's existence need not preclude you from possessing a rational mind. It can, however, occasionally interfere (as it did with Einstein and his erroneous opposition to quantum mechanics based in large part on the idea that God would never be so random or disorganized).
In the end, I don't find the notion of God's existence to be testable, just like my pet pink dragon. To me, the universe simply makes a lot more sense without Him/Her/It, and hence my identification as an "atheist". But to the vast majority the opposite is true, which is okay by me. Just don't cut my head off over it, and we'll get along fine.