I would agree that atheism may not be a religion since it has none of the usual stuff theists consider such as eschatology for instance. But I also would agree that atheism is a religion for it posits a belief taken not on empirical evidence that God doesn't exist. To accept that principle on a matter of faith is a key element in subscribing to a religion. Conversely the same principle can be used to characterize theists except that they remove the "doesn't" from the earlier statement.
Also both theists and atheists would support their position on their experiences. And lately we can see "religious" organization on the part of atheists, with them preaching from Dawkins' "Delusion" and Hitchen's "Not Great".
Is this some sort of selective forces that is needed for coexistence in a human population whose majority are theists?
But as an atheist complains to folks that lump his worldview with that of the theists "if atheism is a religion, then what isn't a religion?"
I would contend that Science is the perfect alternative. In Science we don't believe but just accept (that conclusions will be changed anyway) facts as they stand now. But while atheists and theists may find meaning in their worldview, Scientists can't from the science alone.
And I think Science will show that there are no non-believers in the human population anyway. God is a fiat! And that fiat could be a non-God!
Well it could be that it is surely more harmful to souls to declare a heresy to believe what is proved [ex Scientia]