You're right. Innate instinct has nothing to do with the verity of those instincts. I concede that to you. However, I did not mean to insinuate that innate instinct implies verity, I was simply venting my loathing of religion.
Would you consider it absurd to deny the existence of Thor? How about Zeus? Poseidon, Hera, Minerva, Rah, or any of the millions of other Gods that I can not possibly cover here? Would you consider animism absurd? Your answer to most of these is probably yes. As it should be. Why? Because any form of theism is making a positive claim. And the onus lies with the claimant when asked to prove his claim. If he cannot, then the claim should be dismissed by a thinking person.
People are often confused by what atheism is. Atheism is not a positive claim, it is the rejection of a positive claim that is postulated by some, and inculcated to most of the rest. And as I said before, the burden of proof lies with the claimant, not the skeptic. I know I've posted this analogy before, but the theism scenario's absurdity is summarized by Bertrand Russel's teapot analogy:
If I were to suggest that between the Earth and Mars there is a china teapot revolving about the sun in an elliptical orbit, nobody would be able to disprove my assertion provided I were careful to add that the teapot is too small to be revealed even by our most powerful telescopes. But if I were to go on to say that, since my assertion cannot be disproved, it is an intolerable presumption on the part of human reason to doubt it, I should rightly be thought to be talking nonsense. If, however, the existence of such a teapot were affirmed in ancient books, taught as the sacred truth every Sunday, and instilled into the minds of children at school, hesitation to believe in its existence would become a mark of eccentricity and entitle the doubter to the attentions of the psychiatrist in an enlightened age or of the Inquisitor in an earlier time.
Now, if you still don't see why, I think this argument should be broken down mathematically. Theism essentially is an explanation for the existence of life, the cosmos, and everything inside it. But theism is only one of a billion different explanations that can be conjectured. In fact, it's one in an infinite, however I will stick with a billion for mathematical simplicity. One of these billion explanations must be correct. However, we can only lean towards one over the others when one has evidence, otherwise they should all have an equal weight in our consideration. Well, lets assume that this is the case. Lets assume that they all have equal weight (in reality they don't...science is evermore piling on the evidence, and ontological arguments make the God hypothesis unlikely to start with). Then what the theist is doing is claiming that his 1/1,000,000,000 is absolutely the correct one. The atheist is saying, no, it is one of the other 999,999,999/1,000,000,000.