Who's to Say?
Let’s say moral value is just whatever we say it is. If this were true, we would have to give up the way we normally think about morality.
Say you had a disagreement. Let’s say 50% of the people on the planet thought that lying was OK and 50% thought that lying was wrong. Now which is it? Is lying right or is it wrong?
Well, there’s no fact of the matter in this case; it just depends on what you think. To claim that lying was is wrong would be like saying, "You know what? Vanilla is definitely better than chocolate. And you are wrong to say otherwise."
That would be the logical ramification of not having an objective morality . . . and we would just have to learn how to deal with that. If there's no objective morality, we simply can't go around saying, "No, I am right. You are wrong."