Erin, my husband is not at all religious, but he does believe in God. He's very active in adult training in Boy Scouts. He's an Eagle Scout himself. I am decidedly unhappy with their anti-gay policies, and if it were me, would stop helping and make sure everyone knew why.
But the atheism.... He knows how I feel. We don't talk about it, probably because religion doesn't come up much. With most people, discussing their beliefs, I have little respect if someone tries to "prove" anything to me, because when I was Catholic, I learned that "faith" is the key. There IS no proof. Faith is held up as a lofty goal, something to strive for, because you have to take that final step with complete faith. Philosophers and theologians have danced around this for ages. Nobody can prove to you that there is a god. So if I were to discuss it with someone, and maintain a friendship, they would have to be willing to admit that there is some faith there that they are willing to accept, and that I do not. I'm okay with someone admitting that.
Like you, sometimes I think we don't have a lot in common. The kids are about to leave the nest, so we might find out soon how much that meant. But we just spent two weeks in Atlanta together, going through his parents' home, and it went very well. So who knows.
I'm glad you've posted here. I'm not sure I was any help, but I hope you can come to some kind of understanding. Mutual respect, agree to disagree.
DH and I differ politically but neither of us brings it up much to avoid arguments.