If you can refute moral relativism (a task which has eluded philosophers for millennia), they will not only award you the Nobel Prize in Philosophy, they'll create one especially for you.
What would moral relavists think about moral relativism if we tortured them slowly to death and fed them their own children for their own sustenance, etc.? Most moral relativist have simply abstracted themselves from the real world and just need a good dose of it to wake up. Few of them make convincing arguments, because after they deconstructed morality, they proceeded to deconstruct reason. And we know what becomes of argument without reason.
And your blanket statement that it has eluded philosophers for millenia is simply ridicilous.