I've been hearing that for a number of years now, and I don't think it's a religion as much as it is an absence of religion. I think it's faulty to equate Atheism with Humanism. I don't know of any churches with "Church of Atheism" out front. I think we Christians will have to think more rationally and characterize things more fairly instead of coloring it with our pre-decided notions, if we want to be taken more seriously. IMO, "Atheism is a religion" is just one of those things someone said that everyone agreed with, without really thinking about it, just because it sounded like general acceptance of it would make life better for Christians in the political arena.