Portmore is taking aim at subjective utilitarianism and everything he's said is true ... until he gets to the comments. I'm not sure he's wrong, but I'm not sure he's right. The issue? Consider:
"those who perform objectively impermissible acts because they are culpably ignorant of the relevant non-normative facts are just as blameworthy as those who perform objectively impermissible acts because they are culpably ignorant of the relevant normative facts"
I'm not sure. You could say this. The reason that non-culpable ignorance concerning matter of fact excuses (sometimes, most of the time) is that someone who acts on mistaken factual beliefs has not shown that they are willing to act against the values that we should care about but someone who acts on non-culpably ignorant normative beliefs does show that they are willing to act against values that we ought to care about. That the judgment is itself non-culpable just shows that they have not shown themselves to be willing to shirk epistemic responsibility. Thoughts? I need feedback.