Over the years I've been part of a few debates on nature of ethics. A common issue is whether right and wrong exist in some objective perfect sense. Strange sounding (to modern ears) passages from the Bible and different moral norms in different societies undermine faith in unchanging moral standards. A common counter is that the fact that we don't know all the answers doesn't mean that they aren't out there.
I don't believe that giving up your belief in this ideal should result in moral relativism or nihilism, but I think it's striking that a lot of our morality seems dependent on our peculiar biological nature and our level of technological development, so we shouldn’t expect aliens or artificial intelligences to have similar ethical ideas and this shouldn’t make us think that this makes them evil.
There are lots of examples of what I mean, for example many moral rules, especially in the past, concerned food and its preparation and there would be no reason for aliens to care. But we shrug off the weirdness of the past as if it were no big deal, but look! Something used to be immoral and no longer is!
But I’ve been thinking of one example in particular, which concerns sex. I’ve often thought that sex was overly moralised compared to the ethics of driving, say. The thing is that back in the day the consequences of having sex were just much bigger. Having sex meant risking pregnancy, disease, economic ruin and the excellent chance that either mother or baby would die during childbirth. And there wasn't really much you could do, condoms only became widely (and cheaply) available in the 30's, the Pill hit the scene in the 60's and a hundred years ago and earlier just about everybody was poor. So it made sense that there should be a strict code of ethics governing sexuality which was enforced with severe social penalties for transgressors. These rules used to mean the difference between a society dying or flourishing.
Technology has radically reduced the expected cost of a sexual encounter and western society is now very rich and robust, so these worries just aren't the same.
The point is. If the consequences of an action change, it changes what counts as moral or immoral behaviour.