The Bellman said:
Firstly, a set of moral standards laid down by god wouldn't be objective - they'd still be subjective, just from HIS point of view, instead of any human's. They might (arguably) be a better (or worse) set of moral standards than others, but they'd still be subjective.
And if there were ANY way of proving - or even evidencing - that a particular set of moral standards actually came from god, then you might be able to prove that such a thing exists. But since there is no way of evidencing such a thing, the idea that it exists at all is without supporting evidence.
NATURE proves the the rightness of God's laws! One example is that the anus was not created for penile insertion which is why anal sex causes disease! This elementary principle is simply not understood by unbelievers. CHILDREN understand that! but the sex drive reigns supreme so people constantly look for ways to rationalize why there's nothing wrong with anal intercourse.
I will list how God's laws can be proven.
1. if we don't love God above anything else, then we will eventually destroy ourselves through VD, murder, stealing, power, etc.
2. If we put other gods before him then we will worship money, success, greed, etc. which leads to all of the above.
3. If we don't set aside a time to rest and meditate over God's laws, then we will succumb to the above.
4. If we bear false witness then we fall into deception which leads us to not know right from wrong, who is the enemy and who isn't, and which "god" to follow.
5. If we don't honor our parents then we have zero respect for those who have already lived through what we have and spent night after night and day after day taking care of us. We will then have zero respect for human life.
6. Hopefully people know why murder is wrong, but if people don't know why the other commandments are wrong, i doubt they will understand why murder is wrong.
7. Coveting leads to stealing.
8. Adultery leads to degrading our bodies for sexual gratification REGARDLESS of what it does to our spouses or families.
9. Coveting leads to stealing and complete ingratitude for what one has.
10. Taking the lord's name in vain is a complete disregard for his creation which means our own lives and the earth upon which we live. It not only desecrates god for these things but destroys ANY chance we can have for salvation.
I feel like a kindergarten teacher having to explain why these laws are the only morals upon which we can perpetuate human life. But sadly, many people, who of course consider THEMSELVES intelligent, (which is the sin of pride) can't understand these basic principles. They believe in themselves and their laws. Well sorry, so far, human laws have done NOTHING but bring us pain, disease, and death.