How about "because it is their right"? It's my right to write a racist novel in which minorities are lynched. It's my right to march down the street screaming that everyone who doesn't find Jesus will burn in Hell. It's my right to view pornography and masturbate until my arm falls off. It's my right to go to the place of worship I choose. It's my fundamental, "don't screw with me because one of my other rights is to own a gun", "none of anyone's business why and if they don't like too damn bad", right to associate with whomever I choose for any reason I choose. The BSA has made a decision, based on the history of their organization as being founded in a male-dominated, Christian society, to NOT ASSOCIATE with athiests because it is their RIGHT. Before condemning the BSA for their choice, we need to closely examine the implications of abrogating those rights. The wonderful, exasperating dichotomy of the American Constitution is that so much that is good can also encompass, allow, and even encourage so much that our larger society finds reprehensible.