You are defining relativism in a way that is inescapable. I challenge you to find anyone in the world who doesn't have some things that they consider 'wrong.' No matter how strong a nihilist you find, he will never tell you he doesn't think torturing people for pleasure is wrong. I don't deny that charge; I consider it 'wrong' based on the way I have evolved. Firstly, the fact that I consider it wrong doesn't make it so. Secondly, that is not the definition of moral relativism, which is what I was defending myself against. Moral relativism is the assertion that the same action can be simultaneously right for one person and wrong for another. A good example would be slavery; were slave owners of two hundred years ago immoral despite the fact that it was an accepted practice?
Nihilism, as I mentioned, is not a practical moral theory in that it doesn't give guidance on how to live one's life. Obviously, by rejecting the claim that truth is ascertainable, it could be self-consistent and still do so. However, it is in our natures to act as if every choice were equally meaningless, and so we search for something to guide us by. I think the basic claims of rational egoism are false (hence my claim to nihilism) but, in the context of the world we live in, I think it is the preferable system of morality. According to the definition you're using, that is relative, and I won't deny that but I will deny that it is moral relativism as it is technically defined.
Menzo