I immediately thought of Ayn Rand when I read this.
I thought you said atheism was merely the lack of belief in Gods. Now you have it as some kind of moral influence.
Oh dear Vlad - once again failing to understand what atheism is.
Correct me if I am wrong, but your quote from BHS never mentions atheism and indeed its focus appears to be religion, which is of course a completely different thing. While atheists do not believe in the existence of god or gods (nothing more, nothing less) we completely accept that religions exist, albeit the presence of a religion that posits that a god exists is no evidence whatsoever that that god actually does exists.
But religions are social structures and although most (not all) are necessarily theistic they cannot all be correct in their theism as many are mutually exclusive in their claims of god.
So the point, I guess, is whether humans can exist without religion. The answer to me seems inherently 'yes' as religion is just a sub-set of societal structures. Plenty also exist, within human societies and as societal structures of closely related social species (e.g. gorillas, chimpanzees) that are effective societal structures but are not religions.
So perhaps the most relevant question is whether humans (and other closely related social species) can exist without societal structures. And here I guess the jury is out - and arguably the answer would be 'no'. Certainly in the long run as evolutionarily we need these structures to ensure that genes are passed on as human (and related species) offspring require that societal structure for basic protection (human babies are incredibly vulnerable for a long time) and also for passing on the very thing which makes our species successful, namely knowledge.
But coming back to whether belief in god is necessary - well I don't think it is, provided other elements that support societal structures exist. Do gorillas believe in god Vlad?
But none of this takes us one iota further in terms of whether god actually exists in any objective sense - god either exists or does not exist and I don't see how any 'belief' in that existence provides any evidence that god actually exists. Certainly for virtually the entire existence of our own planet belief in god didn't exist as that belief requires not just life but life that had evolved with a sufficient level of higher consciousness for that belief to be possible.