I wouldnt say that every act is selfish, I cant agree with that. However, perhaps no act is truly selfless.
Now I said it is for me right not for the next person that is in that way subjective.
But we are looking for an absolute, not a subjective belief. If everything is subjective, nobody is ever truly right with their morals. So do I take it you believe lawlessness is more appropriate?
Certainly some people believe in objective moral standards and that is the reason things are the way they are.
A person who truly has relativistic beliefs could not go that long without contradicting themselves.
If its between you and another person with opposing moral beliefs, you couldnt believe that you are right when there is no right. So somebody does harm to someone close to you, you cant get angry because he wasnt wrong in doing so. You arent right if you believe hes wrong so...... You would have to be unaffected if you truly had relativistic beliefs .
One of the points you might not have read that I have made is that yes people have different beliefs but that doesnt mean there are not moral truths. Lets say I believe you are 6'0" and you believe you are not, one of us must be wrong.
Moral standards are the same in that respect. There is a truth there even though some have opposing beliefs. Even then though there are still some other factors that I have mentioned. Like people interpreting a situation different ways, trying to justify their actions, feelings of guilty, anger at ones actions and so on.
We arent talking about whether you think water or beer is best for you.