Metaethical Moral Relativism (MMR). The truth or falsity of moral
judgments, or their justification, is not absolute or universal, but
is relative to the traditions, convictions, or practices of a group of
I was supposing that Smith's justification can be incorrect, but it is still relativism... that a person justifies a moral judgment with "X" isn't just how they got to know if something is justified, but what the fact that makes their justification successful or not is relative to; and so that fact is not absolute.
As to the second puzzle, if a moral principle is invariant, then that they justify something with "X", must include the relevant principle, and the fact making them right or wrong is always relative to the principle. So (in this meta-ethics) I can no more reject someone's justification on the grounds of their principles, than that they justified it with "X" (i.e. I cannot deny the success of some justification with the charge of incompleteness - counter-reasons against the moral judgment); only e.g. inconsistency of reasoning, false assumptions, or insensitivity to social reality (which would probably amount to the intuition that something is amiss in the the stages they go through in their attempted justification).