It depends on how one defines religion.
What about atheists who have dogmatic adherence to views on:
• The existence of, well, existence (purposeless and unintentional).
• The existence of our universe (purposeless and unintentional).
• The existence of Earth-based life (purposeless and unintentional).
• The existence of human life (ultimately purposeless and unintentional).
• Morality (no ultimate foundation; based entirely on [evolved] reason).
• The (absence of) an afterlife.
…and who:
• Frequently read atheistic literature.
• Proselytize for atheism (including on the Internet).
•
Attend church-like atheist sermons conferences.
I know many people who fit
every single one of the above listed criteria. Should these people be considered religious atheists? If not, why not?
What is it about their strong adherence and devotion to atheism that differs from, say, the devoted Christian’s adherence to Christianity?
Is it simply that they lack faith in God(s)? But, then, religion doesn’t require faith in God(s), as you’re clearly aware of, hence your comment on Buddhism.
What is the demarcation line that separates religion from non-religion?
In my opinion, atheists who fit the above criteria are religious.
On, and one last thing: Religion does not require belief in god. So, if you're argument against atheism being a religion comes down to a lack of belief in god, then you've lost right out of the gate. Furthermore, even if it did, one could argue that nature is the atheist's god. After all, the atheist ascribes to nature all of the powers most ascribe to their god.