The Church says we have to believe in God to have a sincere belief in morality. Another way of putting this is to say that we are accountable to God so we must believe in him and in his laws of morality.
What authority gave God the right to tell us what to do?
How do we know if he is an impartial judge of right and wrong?
How does he work out what is right and what is wrong?
Why is there so much discord between religions and in religions about what God has decreed or wants?
All these are important questions.
Is good good whether God commands it or not? Some believers reply that it is good merely because God says so. Then clearly the believer is admitting that he will regard murdering prostitutes as holy and good if God says so. It is so dangerous for it is really the believer saying so.
The notion that even wanton murder would be good if God commanded it is the divine command theory. 
A religion saying God says such and such is wrong does not mean that he really says it. It could be the religion making the rules and pretending they came from God. Divine command puts us at the mercy of religion. 
If the divine command theory is true ,then the believer who thinks God wants him to eat babies alive should be respected as much as the believer who thinks God wants him to give all he has to the poor. God would not blame either believer for getting the rules wrong as long as they did their best to learn what the rules were.
If God has to consult a standard of right and wrong that is independent of him and autonomous then we have the right to disagree with his interpretation of the standard. The standard matters above all things not him and he is not really the only thing that matters though he says he is.
God either makes good good or he doesn't. Two options. Those who say there is a third option are clearly lying.
Here is the so-called third option.
It is said that good is good because God’s character is good and God's character reveals what is good and is not arbitrary. But is God's character good because God makes it good or is it good because good is good whether God recognises it as good or not and it manifests and sanctions that good? So we are back where we started.
The believers do not worry about the idea that what is good is only good because God commands it because God is loving and so will not ask us to do anything harmful. This is really saying that good is good merely because God commands it. This is the divine command theory again. They also say that good is good whether God sees it as good or not. This is the other option. Its not a third option at all. It is just the only two options rephrased to disguise them. The two contradictory options are deceivingly presented as complementary!
Some theologians say that God does not invent morality though the divine command theory is true. To put it another way, God‘s rules about what is right are not arbitrary. But that is like saying that a lie is not a lie.  Just because a moral rule does not seem arbitrary does not mean that it is really a moral rule.
The "third option" suggests that God will not command us to commit genocide against black people for example. But the fact remains that in principle he can for it becomes good just because he commands it. We are just lucky that he is so good that he will not do it. But we are still defiled by believing in the third option. Hypothetically, we still condone evil. It is evil to think, "God will not command evil things but if he did I would obey him and categorise them as good."
The believers say that goodness is grounded in God's moral nature. Moral means you are bound to a law - and a law without a threat of punishment is not a law at all. He is not like us at all but more like a mind without personal characteristics. So how could he be moral? He is not a moral agent for he cannot be punished if he does wrong. He can't do wrong but that is not the point. God may have a good nature but cannot have a moral nature. Even if you need God to believe in good you do not need him and cannot need him to believe in morality.
Some say that God does not follow a moral standard but does good just because he is good. He has no obligations because he is perfect. These people then deny that morality is morality whether God approves it or not. Religion says that God not being a moral God does not mean in itself that he cannot lay down morality and reward the holy and punish the wicked. It claims that it is not God's fault that he cannot be a moral agent and hence rewarded or punished. But the fact remains God has no need to lay down morality for no matter how bad we get it does not affect him. So he cannot be a moral agent.
The third option claims that what is good and adorable and what we worship in God is his good character. It is alleged that believers do not worship him because of what he commands but because of what the commands say about him as a personal being. They have to say that for worshipping God because of his commands is really just worshipping the commands and not God. To worship Janine's beauty is not to worship her. But to worship God's virtues is not the same as worshipping God either! They can only say that they worship God for he is a person which amounts to saying he is not entitled to any more respect than any person would be. They go on about loving the sinner and hating the sin. They claim that the sin is not the person. But if they love God because of his character that is to say they should not or would not love him if he has a bad character. The doctrine of loving God because of his good character is in complete contradiction to the notion that the person and the sin are unrelated so that you can judge the sin not the sinner at all. In fact the doctrine of God gives us an additional reason to say that bad characters or bad people should not be loved. Not loving them would be at best a necessary evil. Anything however that makes it more justifiable would be bad by default. That is to say, there is enough justification for hating or not loving without bringing in the idea of God with its adding on to the justification.

The Church answers those who ask, "Is morality just whatever God says it is or is it independent of what he thinks?"  It says the question forgets that there is an alternative, that morality is God's nature.  But that is thin and a trick for it did not ask God to confirm this.  Its philosophers came up with it.  It only goes back to basing morality on opinion the thing they supposedly want to avoid.