Dude, I don't believe either. I don't feel compelled to make snide remarks about people who do believe in that stuff. As someone who deals out his fair share of snarky sarcasm, I know full well it requires no effort on my part not to do it. Contempt is why you do it. I generally don't have contempt for people who have religious beliefs. I reserve contempt for people by how they behave. If I've snarked at you, it's probably because of something you said, the way you said it, not because of something you believe.
I agree I need to do better, I disagree that it's contempt. My family are all believers in what I view as made up stories. I agree I can be more civil about it though.