ikabod writes:
both [xians and atheists] take the stand point that they hold the irrevocable truth on the nature of the universe
This risks wandering off topic, so I'll be brief, although I could argue that as RiverRat shows some misunderstanding of atheists in the O.P., and you're showing a different kind of misunderstanding here, it's relevant.
Atheists do not take the "stand point that they hold the irrevocable truth on the nature of the universe". This atheist doesn't even know what the universe really is. It may have more than four dimensions, for example, and appears to be a very mysterious place, even to the minds of our most talented physicists. We just don't have faith in any of the Gods of any of the religions. Xians don't have faith in any of the Gods of any of the religions except one. They do claim to know at least one kind of basic truth about the universe, which is that their particular God created it.