It is crucially important that we feel them to be more than mere expressions of subjective feeling, or fear, or conditioning etc. John Mackie talks of an 'error theory' of morals. We are naturally objectivists until we learn otherwise. Now a subjectivist such as Mackie will say that Moral 'perception' is simply the result of the fact that we feel certain feelings of approval or disapproval when we look at the scientifically verifiable, 'empirical' facts. Moral 'reasoning' on this view, is merely the attempt to establish consistency amongst our moral feelings.
Utilitarianism is one of a number of attempts to render moral judgements 'scientific'.
There are two points to make here. The first is that utilitarianism presupposes but does not establish the objectivity of moral judgements. The second point is that the establishment of 'objective' methods, such as calculating what actions would maximise happiness are not necessary for the objectivity of moral judgement. 220-225. correspondence of true statements with the facts Good. You have most of it here.