And if this 'objective' morality comes directly from God, then that just proves it's subjective.
God commanded killing under certain circumstances, but commanded thou shalt not kill.
God gathered righteous armies for that purpose.
We agreed that God can lie, but commanded against it.
I can agree that there is an inbuilt sense of fairness in us, but we are all willing to forfeit that for the greater good.
It's subjective because objective morality can't ever work.
I don't think that killing is moral, but if future generations depended on it, I would kill.
That's subjective morality.