Consider this article on contradiction:
A contradiction arises when two ideas each make the other impossible. Contradictions don't exist in reality because reality simply is as it is and does not contradict itself. Only our evaluations of reality can contradict each other. If you think you have found a contradiction, then check your premises. Either you're mistaken about it being a contradiction or one of the contradicting concepts has been improperly formed.
If the content of your knowledge contains contradictions, then some of your knowledge is in error. Because in order to be successful in reality one must know reality, success requires correct knowledge. It is therefore important to continually search for and root out contradictions in your knowledge in order to make sure that your knowledge corresponds to reality. The two primary methods for doing this are logic, the art of non-contradictory identification, and integration.
Now consider for a moment that perhaps, under relative and subjective moral standpoints, we do in fact have temporary contradictions that exist in our evaluations of reality. With that being said, we will eventually convene to one conclusion, and thus will eliminate one side of the temporary contradiction.
If we acknowledge the existence of these temporary-evaluative contradictions, then we can begin to accept cultural relativism and individual subjectivism while avoiding the dreaded reality contradictions that usually travels with them.
Hopefully I am making sense so far (though if I’m confusing you then maybe I am just being a good philosopher)…but basically I am saying that yes, contradictions in relative and subjective logic do exist, but they are only part of a momentary battle that wages between moral beliefs, from which eventually the dominant moral rule will emerge victorious.
Do not be quick to see this as objectivism. Objectivism suggests that there are preexisting moral truths that apply to everyone in the universe, and they have not much say in it. I am suggesting that objective truths are made by man and woman and surpass us through a sort of “survival of the fittest moral”.
This could happen in a variety of ways, the simplest being death, brought on by either natural causes or war. If slavery was truly a dominant moral, then the Confederacy would have won the Civil War. If euthanization, religious intolerance, and the use of fear for control were all dominant moral rules, then Hitler would have won World War II and we would all be speaking German right now. Therefore, what is morally right to us now is freedom, the right to live, tolerance of all kinds, and representative democracy. Overall, civilizations with greater morals will live longer than those with lesser standards.
My idea here is not ironclad, but is fun and interesting to try to apply scientific reasoning to that of philosophy. Maybe all of this competition for survival in morals will one day lead to pure objectivism, in which there is no longer anything to fight over and all of humanity will become a hive mind? Would this be a good or bad thing? And if it was bad, under relative and subjective theory, would be even be able to realize our objective morals were wrong if we all would come to have the exact same moral beliefs?