I agree but with some spin control.
It might be that by deducing "B" from "A" and "if A then B" we thereby deduce something false. But then either "A" or "if A then B" must have been false
This is key. I like to say that we play logic with a stacked deck. We've dealt all the aces to a few logical rules. This doesn't mean that logic isn't in some sense absolute, but it removes any whiff of theology that might be suspected to be attached.
Users of a language have to agree on the meanings of primitive words like 'and', 'if', 'then', or else they're just 'playing a different game'.
True, but there is more to being logical than just following linguistic convention. The philosophers' classic "tonk" operator works like this: From A, one is licensed to infer "A tonk B". From "A tonk B" one is licensed to infer B. Luckily for language users everywhere, there is no actual language with these conventions.
lukeprog gave a list of metaethics questions here:
Most of these questions make no sense to me. I imagine that the moral intuitions in my brain come from a special black box within it, a "morality core" whose outputs I cannot easily change. (Explaining how my "morality core" ended up a certain way is a task for evo psych, not philosophy.) Or I can be more enlightened and adopt Nesov's idea that the "morality core" doesn't exist as a unified device, only as an umbrella name for all the diverse "reasons for action" that my brain can fire. Either perspective can be implemented as a computer program pretty easily, so I don't feel there's any philosophical mystery left over. All we have is factual questions about how people's "morality cores" vary in time and from person to person, how compelling their voices are, finding patterns in their outputs, etc. Can someone explain what problem metaethics is supposed to solve?