I guess my concern is if I said, "This depends on your stance on what counts as an epistemic fact, but you should accept the conclusions of a sound argument," what prevents someone from saying, "Well, if it's stance-dependent, then I'm totally justified in accepting unsound arguments."? It seems a person would be equally as justified in accepting unsound arguments as they do sound ones.
Before reading the article: The argument I often hear in support of moral realism appeals to moral experience, but moral experience seems totally consistent with moral anti-realism being true. I don't know what evidence for moral realism would look like even if it were to exist, but that would just mean that there's no reason to prefer either view (anti-realism vs. realism).
After reading: This Cuneo-style argument that Matthew used in this writing is interesting. I forgot about the bad company argument that I learned about several years ago. Don't I lose epistemic facts if I lose moral facts? Maybe so. It seems self-refuting to argue that people should be indifferent to purported epistemic facts; if you want people to clearly assess the merits of your argument against taking epistemic facts seriously, you seem to need them to have rationality. I don't think you'd want them to misrepresent your argument against epistemic facts, use an ad hominem as justification for rejecting it, etc.
Interesting. I'll have to think on this. Thanks for your comments!