I think it quite obvious that if one does not observe a given theory they are not thereby disarmed from criticism of such a theory, similarly, a rejection of moralism is not equivalent with your imputed upshot that “nothing is right or wrong” (although we can imagine cases in which that could be so). In the case of the former, critiquing a theory adhering to but contradicting intuitionistic premises is a straightforward instance of immanent critique. In the case of the latter, quite famously, neither Bernard Williams nor Raymond Geuss had any truck with moralism, yet clearly were not ‘relativists’.
I think it quite obvious that if one does not observe a given theory they are not thereby disarmed from criticism of such a theory, similarly, a rejection of moralism is not equivalent with your imputed upshot that “nothing is right or wrong” (although we can imagine cases in which that could be so). In the case of the former, critiquing a theory adhering to but contradicting intuitionistic premises is a straightforward instance of immanent critique. In the case of the latter, quite famously, neither Bernard Williams nor Raymond Geuss had any truck with moralism, yet clearly were not ‘relativists’.