As an agnostic (the church of I Don’t Know) atheism and religion share a similar characteristic. The “members” are “sure” of something. Religion is SURE there is a “god” and atheists are SURE there isn’t a “god”.
Since neither one can be proven (currently) it seems you’d have to use some sort of “faith” in order to have that kind of certainty. Yea I know we fence sitting agnostics are weird but I think it’s the lack of any certainty in this area which binds us as a common thread.