There is plenty of evidence that proves a universal moral code is completely idiotic. For one, It would require the existence of a supreme being. For how could a sense of morality be incorporated into evolution? The human genome has been mapped, and there is no 'soul'. Nothing that sets us apart from any other species on the planet (Other than the +-2% difference in code from chimps.
Aside from the existence of a god, we know that a person's environment helps to shape his character and actions. If you travel to different cultures, you will find that they do NOT all share moral similarities. Just open a single history book! Ancient tribes were not always against stealing, murder, etc. Ancient civilizations have created games in which if you lose, you die. They have sacrificed other people.. People have fought and killed others for "the glory of god!" People who fought in the crusades thought they were killing on behalf of god, and thus it was morally right. Tribes in Africa and many other places still practice pagan rituals that the western world would consider immoral. The novel okonkwo is also a perfect example. Okonkwo was a wise and powerful leader of his tribe.. They did many 'evil' things such as murder(killed babies that were thought to be evil) and thievery. They followed what their prophet said, b/c they thought it was moral and right. Then the Christian missionaries come along and force their ideas on the people.. Okonkwo ends up committing suicide.
Society decides morality. People are shaped by their environment. There is no universal moral law.. Morals exist only b/c people create them. Again, look at many mass murderers throughout history. Hitler, for example. He truly thought that the Aryan race was supreme, and that all other people were inferior. He risked his own life and killed millions b/c of his belief. He obviously thought what he was doing was moral and just, but people disagree based on their own principles.
Ok, I'll buy that. Several things to consider, though:
1) Being the science/reason-based person you are I'll treat the debate like this. Your very second sentence nullifies this. One must never not consider something becuse of the implications it causes.
In a similar sense, a scientific study that somehow goes against evolution (and yes, there are some reputable ones) arn't automatically thrown out simply because they go against evolution.
2) "The entire genome has been mapped"
While off topic, I will still mention into it. While yes, the entire human genome has been mapped, you must realize that all it has shown is a similiary to other organisms (predominantly apes). However, it's basic Biology to point out that our DNA consists of introns and exons, and we currently do not know the combinations of the exons that produce mRNA. With that said, there are still a pletora of differnet mysteries surrounding the genome. For one, what happens to snRNPs? We still do not know where they go after production.
3) Hitler, etc.> I think we all will agree that Hitler, along with Stalin and the current leaders in Uganda, arn't fully mentally and morally there.