"Natural Laws", "Natural Rights" and Libertarianism.

I can accept this up to a point, save that societal 'rights' also often depend on the circumstances of your birth - the colour of your skin, your sex, your sexual orientation, the religion you're born into or perhaps even the social status you have in the context of your parentage.

Err - has utilitarianism ceased to exist? Last time I checked, I didn't admit natural rights any status greater than (possibly) a useful approximation to allow us to pick the utility-maximizing option (which, ironically, might not be so far removed from certain conceptions of natural rights anyway.) It also has good reason to be anti-child sacrifice and anti-holocaust, by virtue of the wheeze of knowing the result one is supposed to get and skewing ones consequentialist calculus to get there.

This is exactly it, you've cut right to the point: unless you believe in natural rights of some sort you have no justification whatsoever for saying that the Aztecs sacrificing children or the Germans gassing Jews was wrong. All you can say is that it's wrong-as-interpreted-by-modern-western-standards. Are you really willing to accept that in their own context the Aztecs and the Nazis were acting morally?

You're also conflating the two issues of whether natural rights exist as a matter of practice and whether they exist. I believe that the Aztec children and the Jews in the concentration camps did have rights - the right not to be murdered, for example - which were of course infringed. Which is why I feel I can say that the Aztecs and the Nazis carrying out these deeds were acting immorally. Can you, as someone who doesn't believe in natural rights, say that?

Yes he can. Can you not see that natural claims don't make sense. It's just a whole lot of stuff you'd think would be nice. But they aren't authoritative in any objective way. Morality doesn't need to rest on natural rights.

I don't see how any single one of the alternatives are not. Utilitarianism? I think it would be nice to minimise suffering/maximise happiness (whatever they mean and however you measure them) therefore that is what's moral.

This is exactly it, you've cut right to the point: unless you believe in natural rights of some sort you have no justification whatsoever for saying that the Aztecs sacrificing children or the Germans gassing Jews was wrong. All you can say is that it's wrong-as-interpreted-by-modern-western-standards. Are you really willing to accept that in their own context the Aztecs and the Nazis were acting morally?

You're also conflating the two issues of whether natural rights exist as a matter of practice and whether they exist. I believe that the Aztec children and the Jews in the concentration camps did have rights - the right not to be murdered, for example - which were of course infringed. Which is why I feel I can say that the Aztecs and the Nazis carrying out these deeds were acting immorally. Can you, as someone who doesn't believe in natural rights, say that?