While
Nassim Taleb would disagree, religion to me = faith-based philosophy. To me, the term
atheism misses the point, but there is no exact term in the common lexicon (e.g., areligious or afaithful), and I'm not one for pedantic neologisms. Ultimately for me the question of atheism vs. religion is an epistemological one, namely is knowledge properly gained solely via reason (atheism) or also via faith (religion).
IMO, faith (belief in the absence of evidence or in the presence of contrary evidence) is diametrically opposed to reason. Saying "God does not exist" is less a dogmatic statement, and certainly not a statement of evidence-based fact. It is shorthand for "there is zero evidence for God, and an omnipotent/omniscient God is a logical impossibility, therefore I'm going to live my life as if there is no God, and
not believe in his existence."
Alien claims, like most God belief, fall into the
not even wrong category.