If we saw a lot of black crows (and no other kind) we might well believe that all crows are black, if we wanted to; but we could quite rationally (although we would naturally find it quite absurd to) believe in Humean Supervenience, and hence that there was no evidence for such a belief (and either way the albino crow would come as no great surprise). Facts, in other words, are what we want to believe—we want to believe the facts, because we value truth; and truth is useful, but what about when it isn't? On a Naturalistic view of humans, we value truth because to do so is so useful, in general, that primitive hominids that didn't do so died out; whence we value it even when it would be more convenient for us not to. Facts force themselves upon us as true. Snow is white, it seems, whence we believe that it is.
......That tree is pink with blossom—is its pinkness (as it seems to be) something that is out there, in the world, or is it in our heads? Naturalists believe that only the photons are out there (or rather, somewhere that corresponds to the "out there" that is similarly in our heads). And does the objective reality (for Naturalists) of particles in spacetime contain some thing that is that tree? Logically that seems unlikely; but still, does it really matter? Such is how reality is represented in our brains (evolution has probably led to the world as we perceive it being a good enough map of reality for our natural purposes). Winter seems to be closed in on itself; loved ones seem to shine—such a useful map, and presumably evolution has similarly led to moral axioms being included in our mental maps.
......Having in it some moral axioms (such as the Golden Rule) would have similarly aided our survival, as would a tendency to accept the more local rules; we value loyalty, as well as objectivity (and hominids too lacking in either would have died out). So maybe a propensity to form such beliefs as that God is watching us arose naturally. Does such a God exist, the Naturalist wonders; but still, why worry about that? Such a belief should help the worst of us to behave better (and to be more readily identified, and possibly corrected) and anyway, the best of us regard the evidence for its falsity as inconclusive. But (the Naturalist persists) surely it matters whether or not that belief is true? Well, if it's part of our natural representation then surely (for Naturalists) it's at least as true as that that tree is pink.
......The human paradox is that, even were Naturalism true, the value of our natural beliefs in something like God (assuming that we humans have such beliefs) would hardly be outweighed by the value of such objectivity as we could ever attain. We do of course value truth, but many atheists do value loyalty more (in the confusion out there), while many believers regard the Naturalistic versions of objective truth (e.g. scientific modelling) as mere shadows of objective reality—if the truth is that God is watching us, then there really could be an objective truth, one worthy of our valuing it absolutely (and there could more easily be some logical object that is that tree, only approximately analysable into particles).