I've got much better example of situation (hypothetical) when rape would be permitted (or even desirable).Imagine introducing the law using rape as punishment for a sex offender.If there we would conduct a poll asking people if they would support a such law, I think the results would show that at least some people's "morals are not absolute" in the case of rape.Situation quite similar to death penalty or war casualties.
“Before we kill everybody off ah, we just wanna have a little more fun here, if you will rape a woman, then we will let the rest of the species go, okay? We’ll let every, we’ll just leave....."Is Dan Barker stupid? This doesn't make the rape in this case a any less immoral. It's the aliens that are committing the immoral act because of their coercion. In other words, it is both the man and the woman that are being raped.