Richard Posner: No no, no, no, no. Most of the things you list are things that I would regard as immoral, profoundly wrong, criminal. Not everything. I don¹t have particular concerns about pornography. for example. But all I mean to say is that these are judgements we make from our standpoint in terms of our values in our society, not necessarily universal.
Ben Wattenberg: But like you mention human sacrifice.
Richard Posner: Right, well I'm thinking the Aztecs. Well for us, of course, it's not only offensive, it's bizarre. But in an Aztec context, if you were an Aztec (laugh) in the sixteenth century and we come to you and say, you know, "human sacrifice is a bad thing," in their world, in their world view, they will answer you back and they'll say, "well that's what you think, but we have this system of beliefs in which human sacrifice is central." So I don't think we should exaggerate our ability to appraise alien customs from some universal standpoint and say that's wrong.
Ben Wattenberg: I think in that list what I didn't finish was you made roughly the same point about the Nazis, that we could abhor what they did but that was within their value system killing millions of innocents.
Richard Posner: What the difference is ­ and I think this is relevant to the Nazis and also to the Aztecs--some of these alien beliefs are based actually on factual claims. And if the factual claims are false, then you have a real basis for criticism. You don¹t say, "the Nazis are cruel, they¹re savages," you say, "look they had, they founded their ideology on erroneous views about race." Similarly if the Aztecs believed that human sacrifice makes the crops grow faster, you can point out to them, "no, that¹s incorrect." Now if they back up and say, "well even though we were convinced it doesn't make the crops grow faster, still we believe it's a good thing, their souls go to heaven fast," or something like that, we can¹t really argue with people like that. They¹re arguing from different premises.

from transcript of episode of Courting Controversy