Hmm...actually, the implicit assumption I was making was that aliens would forgive another species for adopting norms that they considered non-predispositive.

A Western human would not forgive another culture for torturing sentient beings, for example...but they would forgive another culture for polyamory/polygamy/polygyny. A human can make the distinction between morality which is instinctive and morality which is culturally constructed, and the latter can be compromised in certain contexts.

But you are right, bad implicit assumption. Aliens might not make that distinction.