Yea but if God commanded it, who are you to question it? God is perfectly objective, we are not
Insert: Does God command what is good or is it good because god commanded it? I believe most Muslim scholars say ..because God commanded it, which doesn't make it objective at all. It becomes the whim of God, and we only have his ( or her) word that he is objective. Well not his word because he or she has never talked to us. We have what other people say about God.
That's a weak argument because there is nothing objective about it, and many of the things in "holy books" are pretty horrific. The old saying about it taking religion for good people to do bad things still applies.