I have a problem here. I do not see this question as valid. I see the valid version as “Why would an Atheist perform a task which does not reward himself?” ( long-term or short term)
It does reward us, simply not with a “place” in heaven.
For a simple example, one might say if we choose not to steal, then we are trying to create a community of trust and sharing. This is a much better way to live than stealing…since if we steal, other’s can steal from us as well. Do we REALLY want to spend our time simply protecting what we have?
I agree with the Golden rule, I just don’t think it comes from a God, but rather from human beings that have to a degree determined what makes us live together in a way that is beneficial for us and the world around is.
From a deeper perspective, thinking well, and trying to live well makes us stronger and more competant in life, which in turn enables us to help create an even better home life, community life and human society in general.
I AM a selfish human being. I’ll accept that. I want a world that is nurtured by man and not destroyed by us and I will selfishly do what I can to try and achieve that, even if it means delaying gratification and choosing to give up things I really want.
I have seen friends of mine, fundamentalists, who will do what their “church” tells them because of a reward they are promised to recieve. I see very little thought put into what they are actually doing. When I ask other christians about it, they say “well he isn’t really christian” and wipe their hands of it.
I think if you are honest with yourself, you will at least admit that “believing” in a God, does NOT make a person a good person, nor does any one religion, or denomination within that religion. Even within Catholisism, people venemently disagree with one another.
And a non-believer , can be a decent human being without a belief, and we can read things like “sermon on the mount” and agree with it’s basic message. We don’t need a God, to recognize what is good.
Human nature is SO incredibly complex. Just because we don’t alway’s understand one another, doesn’t mean we have to make-up the answers so that we can keep a solid world-view in front of us.
Perhaps you can simply say “you don’t understand where the athiest moral compass comes from” instead of denying it actually exists.