More Words, Deeper Hole

I don't see anything especially odd about it. It's certainly no odder than associations for unschoolers or free-love advocates. Anyone whose ideas are out of the mainstream can benefit from a community for emotional support and exchange of ideas about how to exist in a world that is inclined to look askance at you. Also, there's a difference between atheists who see at least some forms of religion as essentially harmless and those who think all belief in the supernatural is harmful and should be fought against. The latter are naturally going to be more inclined to be evangelical, and evangelicalism generally requires some organization.