D.H. Monro on Subjectivist Definitions of Morality"The Definition of Morality" in Empiricism and Ethics (Cambridge University Press: 1967), pp. 143-4.
One suspects that some modern philosophers have used the device of defining morality as a means of softening the rigours of subjectivism. They are unable to accept an objectivist ethic, and feel forced to conclude that moral utterances merely express attitudes that men happen to have acquired. They are, however, reluctant to accept the consequence that they have no reason for condemning the moral attitudes of (say) Hitler except that they do not happen to share them. They try to avoid this conclusion by saying that it applies only to certain kinds of attitude. Others may be excluded simply because, by definition, they are not moral. ¶ It is clear, however, that to say … that moral desires are, by definition, those impersonal desires which we want others to share does not excuse us from saying why we think that personal desires should yield to impersonal ones, when they conflict; nor does it justify us in condemning another man if he prefers to give precedence to personal desires. Again, to say … that moral principles are, by definition, ‘universalizable’ does not automatically justify a preference for universalizable principles over ones that cannot be universalized. The hard questions for subjectivism still remain, however morality is defined.