A redated post.
I had a teacher at Arizona State who told me that in one culture rape is considered perfectly OK, so long as you do it at the right time. In the morning, it's forbidden. In the afternoon, it is frowned upon. At night, it is perfectly OK, since a woman who is away from the protection of her husband is asking for it. (He never said which campus fraternity he was referring to).
If cultural relativism is true, the rules of that culture, with respect to rape, are justified. There is no "court of appeal" that is over and above that culture and out culture that would permit us to say that their views on rape are wrong and ours are right. For us to suggest that they are "really" wrong in permitting rape is to elevate the rules of our culture to a kind of cosmic status they cannot have. It is to be intolerant.