YOU must believe in the possibility of your false intuitions

'Good. or bad   falls between the Occamist (apply the razor) argument and the Argument from Relativity. 

It goes like this. People disagree in their basic evaluations. So even if you think your own intuitions are correct owing to your acquaintance with the good, you must believe in the possibility of false intuitions, in which people wrongly perceive goodness to inhere in states which are, in fact, bad or indifferent. These mistaken intuitions are presumably due to natural causes, to upbringing, indoctrination, temperamental bias and so forth, resulting in you inventing right or wrong. 

Moral judgements, specifically judgements as to ends, motivate. There are two possible explanations for this fact: 1) the realist  explanation that non-natural properties of goodness and badness somehow impinge upon us, giving rise to moral beliefs, which, in turn, give rise to desires, and eventually to action; and 2) the emotivist explanation that when it comes to ends, moral judgements somehow embody desires and impulses, and hence give rise to action.