Since all kinds of feelings are equally powerless to "prove" the existence of an objective reality, yet are used as evidence for objective reality in many OTHER cases, they can also be used in the case of feelings of morality.
Well, Holmes is right that that's a fallacy, but the fallacy is the fallacy of
tu quoque ("you too"); in other words, just because your opponent puts forth fallacious reasoning doesn't mean that it isn't also fallacious when you do it, too.