The definition of "religion" requires belief in a supernatural universe,
No it doesn't. While that is a common trait of most religions, it is not required in the definition. For example, the entry at dictionary.com :
"a set of beliefs concerning the cause, nature, and purpose of the universe, especially when considered as the creation of a superhuman agency or agencies, usually involving devotional and ritual observances, and often containing a moral code governing the conduct of human affairs. "
Note that such is explicit that belief in the supernatural, while typical, is not required.
The reason atheism isn't a religion is that it doesn't amount to any positive set of beliefs about the cause, nature and purpose of the universe, nor does it have any of the rest (devotional or ritual observances, moral code). "Atheism" is simply a catch-all term for people who do not believe in god(s). It says nothing about whether those people are religious or not.
Moreover, "atheism" doesn't require any rejection of the supernatural, as such. Only the belief in deities. You can still go in for ancestor worship, or believe in Leprechauns, or whatever, as long as there are no Gods in the picture. While rejection of the supernatural in general is typical of atheists (just as belief in the supernatural is typical of the religious), there is no hard requirement there.
Your assertion has been peer-reviewed and falsified. Do not repeat it on SciForums, ever again, on any thread, in any subforum, or you will be guilty of trolling.
And does this warning apply to you as well, since you are yourself advancing assertions that have been peer-reviewed and falsified? Since you, indeed, make a habit of doing so with several different assertions, repeatedly and in the face of clear, good-faith correction, can we go so far as to outright label you a troll?
Or is there perhaps some salient distinction between adherence to a position in the face of opposition, and trolling? Every coherent definition of "trolling" that I've encountered had as its primary component something about a desire to elicit certain emotional responses from an audience (and nothing about being "wrong," or rejecting consensus, as such).
The problem is that this particular glue only works up to a certain size job.
Does it? It's not clear to me that a one-world religion, with a single nationality based thereupon, is impossible. It's also not clear to me that the process of handling bigger jobs requires replacing religion, rather than grafting something new on top of it (the same was religion works on top of smaller-scale group loyalties in doing the same trick at a smaller scale).
Now that the "coherent identity groups" number in the billions, the religious differences between them work to create antipathy rather than harmony.
That was always the case - and it's a feature, not a bug. Religion is only supposed to create harmony and solidarity
inside the in-group - and thereby empower them to better resist and displace competing groups. Antipathy towards Others is simply the other side of the group-coherence coin. Surely you don't imagine that inter-religious conflict is some new phenomenon that wasn't an issue until the populations got this large? The empowerment of said competition is exactly what led to the proliferation of religion to begin with.
The nation-scale political organizations that actually do rely on religion are proudly and energetically planning to engage in nuclear war.
Exactly. That's a testament to the power of these modes of organization - they can mobilize large populations and resources, with sufficient backing to pursue very high stakes conflicts against other very powerful groups. Less powerful modes of organization don't stand a chance, against that - and so, the more capable modes proliferate.
What more evidence do we need that religion--at least the popular monotheistic variety--is an artifact of the Stone Age that has long outlived its usefulness?
We'd need to see the scale of political organization reverting to that of the Stone Age. Since (organized) religion is still producing ever-more-powerful and competitive political organizations, it seems that its usefulness is not at any sort of end.
Rather, it seems that the Age of Global Enlightenment that you seem to be speaking to, has not yet seen its dawn. It will have to produce some identity politic capable of subsuming religion, ethnicity and nationalism, before it exists in any positive sense.