Cultural relativism is certainly a valid school of ethical thought — one with which I happen to disagree. On matters like piracy, which is certainly less detrimental to society than slavery was, the consequences for believing what is popular and what is right are relatively low. But to suggest that you can apply this principle across the board, in all situations, is, in my view, absurd.

You're suggesting there that we cannot judge anything that has happened in the past because our views on the matter are now different. But that means we cannot judge ANYTHING that has happened EVER because, by definition, now is different from then.

> You shouldn't be convicted that your morality is absolute and will always be the only correct one.

I'm not. I'm just not convinced that, because a certain activity is widespread, it is therefore morally correct.

What I try to say is that you can't judge both piracy and slavery from your present point of view. I feel that because in the past slavery was commonly accepted, that it was morally justified then. In the same way, given the huge proliferation of piracy, I feel that copyright infringement is somewhat morally justified now. This view might change and in the same way, the morality of piracy might change too. I would take the common views of society as the definition of what is morally justified and what isn't. It is possible you see this in another way and that is fine (and not absurd).

Also, this change in zeitgeist is continuous, not as discrete as you overstate it is. We are perfectly justified to judge what has happened yesterday. Judging what happened during World War II is murkier and judging what happened when slavery was still extant is an almost meaningless activity.