Saying that atheism is a religion makes as much sense as saying that theism is a religion. Neither of them are religions, they’re precursors to religion. I consider myself an atheist, but simply stating that I lack a belief that there is a God doesn’t itself become a fundamental part of my personality. Sure, there are people out there who get obsessed with the philosophical and social aspects of atheism, and they let it consume their whole personality, but I wouldn’t call fishing a religion just because somebody has an aberrant proclivity for it.