I never knew that atheists had churches !
I'm a big admirer of the Sunday Assembly because it doesn't seem to tolerate hardline "Religion is stupid" stance. It's not an "Aetheist" church....it's a non-religious Sunday gathering, more humanist in it's outlook.
By joining together as a group, their "God" has become the antithesis of their claims. If they were an agnostic church, however....
atheism.com explains it, but they leave out the bit about worshipping a code ie as if deity, Man U, anyone?