Should we judge the actions of people in other cultures (present and past) by their ethical standards or our own? If we judge by their standards, what must we think of people who follow our mores but break those of their own society?What does it mean to "judge"? We cannot impose punishment on, or give reward to, people who are already dead, or who live in a country over which we have no influence. When it comes to the latter, we can only possibly go to war with them. Judgment tends to be used to facilitate such war.
Having private thoughts of approval or disapproval has no consequence unless it influences actions of the person having such thoughts. Publicly voicing approval or disapproval only has consequence if it influences currently living people's actions.
When viewed this way, judgment of people in past times, and contemporary cultures beyond our reach, is necessarily masturbatory. When we "judge" them, we do it in the same way we might judge fantasy characters. We do it to influence the thoughts and actions of the people we can reach - that is ourselves, and people sharing our space and time.
When it comes to judging people, experience shows that we will judge them hypocritically. Humanity tends to use ethics as a smokescreen behind which to hide our personal interest. The ethics standards to which we hold other people tend to be discarded when it comes to ourselves.
I think we should be very careful about whom we judge, and why. Judgment in general tends to be hypocritical and destructive. We should rather attempt to influence the world in a way we think is for the best, but we should be open to the possibility that we're wrong, even in that case.
I think the answer to this question is: why judge in the first place?