"Our life is shaped by our mind; we become what we think. Joy follows a pure thought like a shadow that never leaves."
― Buddha
Buddhists are atheists, buddy.
Buddhism is a nontheistic religion. In the Gallup data in the OP they fall under the catagory of non-Christian religion.
Given the target audience who better to challenge to words of one agnostic then those of a wiser agnostic.
http://www.religionfacts.com/theism/buddhismOne doctrine agreed upon by all branches of modern Buddhism is that "this world is not created and ruled by a God." {1} The Buddha himself rejected metaphysical speculation as a matter of principle, and his teachings focused entirely on the practical ways to end suffering.
On the other hand, the Buddha did not explicitly rule out the existence of a God or gods.