If the only reason they think that is immoral is because a 'god' tells them it is then they have some problems.
I think you might be missing the point a bit. Your response "if that's the only reason they think its immoral" implies you're referring back to a bigger, more obvous sense of morality. The whole question here is WHERE does that sense come from? And why does it refer to the biigger picture of "right" and "wrong" instead of the more obvious "works" and "doesn't work," or something like that?
In a way, your comment is evidence of what I was talking about a while ago...that we have in us a sense of the moral that transcends day to day experience, and provides some clues to the bigger picture.
And for Xathur, mntman, SD, and others - RL has kept me from the boards lately (obviously I'm not sitting there clicking refresh continuously!). You guys have made seom really good comments. and I jsut don't have the time to respond well right now. Will try to give the time those ideas deserve soon...