"the more sensitive the topic under discussion, the more careful you have to be to avoid offense."

You assumption is that one would want to avoid offense. (note that I don't mean 'not cause deliberate offense') Western newspapers were told to not run the Mohammed cartoons, so as to 'not cause offense'. Feel free to defend the position that people shouldn't make rape jokes, but basing that on 'you shouldn't cause offense' is not an argument.