I would suggest that, in truth, atheists, being relativists, have no moral code. They only have a set of malleable rules that are adjusted/perverted to meet their convenience in a particular situation.
Really? Have you ever stoned your neighbor for working on a Sabbath?
Have you never yourself, lied, stolen, cheated, or hit someone in anger?
Have you ever served in the military or worked for defense contractor?
Have you ever looked at your best friend's wife, girlfriend, car, boat, whatever and thought "Damn!"?
I'd go on, but I think you get the point. Morals are malleable by nature. Codifying them as if writing them down makes them somehow mean something more only increases your own angst when you fail to meet unrealistic goals. There is a certain level of smugness when you cite your morals and compare them to mine which I find irritating because we all know that NO ONE follows that code - no matter where it comes from - 100% of the time. I take responsibility for my own actions and have to answer to myself whereas Christians have already been forgiven for the things they may do and aren't forced to accept responsibility at all. This makes your morality superior to mine? I don't think so.