I don’t think it being unfalsifiable is a problem. I think this is more of a definition than a derivation. Morality is a fuzzy concept that we have intuitions about, and we like to formalize these sorts of things into definitions. This can’t be disproven any more than the definition of a triangle can be disproven.
What needs to be done instead is show the definition to be incoherent or that it doesn’t match our intuition.
Robin, or anyone who agrees with Robin:
What evidence can you imagine would convince you that AGI would go FOOM?