IEPB: “People ought to do X” is your preference because you are assuming “People ought to do X” is a moral fact. It’s a different issue whether your assumption is true or false, or justified or unjustified, but the assumption is being made nevertheless.
If my mental model of moral philosophers is correct, this contravenes how moral philosophers usually define/use the phrase “moral fact”. Moral facts are supposed to (somehow) inhere in the outside world in a mind-independent way, so the origin of my “People ought to do X” assumption does matter. Because my ultimate justification of such an assumption would be my own preferences (whether or not alloyed with empirical claims about the outside world), I couldn’t legitimately call “People ought to do X” a moral fact, as “moral fact” is typically understood.
Consequently I think this line of rebuttal would only be open to Boghossian if he had an idiosyncratic definition of “moral fact”. But it is possible that our disagreement reduces to a disagreement over how to define “moral facts”.
For example, when you exhort IEPB to not make mediocre philosophy arguments, and say that that’s your preference, it’s because you are assuming that the claim, “philosophy professors ought not to make mediocre philosophy arguments”, is in fact, true.
Introspecting, this feels like a reversal of causality. My own internal perception is that the preference motivates the claim rather than vice versa. (Not that introspection is necessarily reliable evidence here!)
Correct, I would call that a category error.
One’s view of the wrongness of torturing a newborn versus soothing it depends on one’s state of mind, yes.
If I were confronted with someone who insisted that “torturing a newborn instead of soothing it is good, actually”, I could say that was “wrong” in the sense of evil, but there is no evidence I could present which, in itself, would show it to be “wrong” in the sense of incorrect.