I didn't say anything about meta-ethics; I said that human brains require emotion in order to prioritize their thinking... no matter how much you might like the case to be otherwise. The brain with which you seek to devise some sort of extra-emotional calculation requires emotion in order to perform those calculations.

That doesn't say anything about the content of the calculations themselves, however. Your brain needs emotion to learn chess or play it... but that doesn't mean that chess itself is emotional. So there's your escape hatch.