However, I don't think the moral relativist argument that not all societies have the Golden Rule , therefore it is not a universal principle, is a very strong argument.
This is like saying that Pythagoras discovered the mathematical theorem that bears his name, and we have evidence that Chinese and Persian mathematicians also discovered it independently, but not all societies discovered it, therefore is is not a valid mathematical theorem.
Are you then saying that morals are not part of what we are. Morals are something that must be learned. I always thought that the moral argument had to do with the idea that we have morals regardles of what we've been taught. If you were to raise a group of people in a sheltered situation and not tell them about the word of God etc, would they not have morals, then when you teach those people morals will they then become moral? What makes the golden rule a universal principle then? Is it because its in many religions that have managed to gain numbers?