Does Morality Depend on the Existence of God?
"I cannot see any force in an argument to the existence of God from the existence of morality" Christian apologist Richard Swinburne.
Playing with words

Objective morality means that some actions are really wrong. It rejects the notion that right and wrong are really only about preferences and opinions.
Hitting a child for no reason really is wrong - it is not a mere opinion.

God to be God, to be perfect and to be worth caring about more than anything, has to be about objective morality. If morality is separable from God then God is not God. Morality comes first not God.
The argument linking God and morality is:
1 If there is no objective morality then there is no God.
2 Objective morality exists.
Conclusion: Therefore God exists.
But what about:
1 Objective morality exists.
2 If there is no objective morality then there is no God.
Conclusion: Therefore God exists?
A valid argument works no matter what order you put the premises, 1 and 2 in. You will notice that the first version looks strong but in fact is not. It is a trick with words.

The second version proves that the argument is assuming objective morality exists and it is doing it without bringing God in. Then it brings God in after. The argument plainly shows that objective morality can exist without God. You can assume objective morality is real morality without involving God.
The absurdity of the argument
Religion says there is no objective morality without God. In fact if there is objective morality, God has nothing to do with it.
If objective morality exists, it does not follow that there is a God.
The argument for objective morality meaning there is a God makes the same errors as
1 If there is no air there is no life.
2 Air exists.
Conclusion: Therefore life exists.

The worrying thing is that extremely intelligent people still dish out the argument that objective morality means God exists. That is deliberate deception and they do it because they know that a large religious audience wants to hear it and lap it up. It is a prime example of a useless argument that has been exposed over and over for centuries and they still keep repeating it as correct and valid.

Opposites ground morality not God

If doing good to a child is stupid if there is no God then harming the child is stupid too. Both actions are different. They are opposites. Both cannot be equally stupid. For that reason alone and it has nothing to do with God, if helping the child is stupid the alternative is worse. It is a brute fact that both cannot be equal. Morality then comes from a brute fact. A brute fact needs no agent to create it. It just exists. Morality is a brute fact. To try to get away from that with the notion of God is to counterfeit morality.
A Disgusting Question
God says we must do good. Is good good just because he says so? Or is it good whether he says so or not? Religion asks how we can say we can be good without belief in God.
Are we to suggest that a person who does not know that God exists does not really have a morality? The suggestion is an outrage.
Our gut instinct is that you are a good person if you respond to your instinct protect a baby from harm. There is something not right about asking, "Is letting a baby suffer not the best thing to do, is it the best, or does it not matter? If the best thing is to save the baby then why?" It is as if you are trying to argue yourself into believing in right and wrong. Forget the justification for helping and just help. Helping a baby is right because it is in its nature. Asking why it is right is like asking why is white bright!
Religion is using God to interfere with your good gut instinct so it is bad.

If your value is to feed the poor that is good. If it won't become your value unless you believe in a God who commands it then there is something wrong.

You shouldn't need a belief as a crutch to give you the value. It means you don't value it at all but have to find a way to imagine that you do. What happens when the scales fall off your eyes? The belief is made more important than the value. Yet reason says a belief cannot be more important than liking to help the poor.

Some will answer that they are not saying you cannot have the value without belief. They say you need to explain why you have the value and the only answer is God. We have already disposed of that nonsense.

Religion tries to get us to base morality on God. All that can do is discourage us and maybe rob us of our whole potential for it is unnatural. It implies too that we must put consciously thinking of the theory first to test ourselves to make sure we are in accord and harmony with it.  The God botherer when lives are to be saved and every second counts will pause anyway to check out his spiritual or religious state. And if the theory is false, it takes away from the goodness of our intentions. What would you think of a person who would not do good unless they were commanded to do it by a God, person or a principle?

Why God?
If there is need for a commander, why does it have to be God? Is it because God knows all things? Or is it because he has infinite power and all things depend on him to exist? Is it because God is perfectly good?
If God has to know what morality is then morality is independent of what God knows or thinks. Murder is wrong even if God, hypothetically, does not know it.
If it is because God has power and makes all things, that is might as right. And God has no needs for he is imperishable and eternal and perfect. So he has no right to expect anything back for creating us.
If it is because he is perfect then we are to take his word for it that he is perfect. If we decide that, means we are claiming to be wiser than God. We are in a position over him and can judge him perfect.

It does not make sense to say that there is no objective morality unless there is a God. Introducing laws and commands only worsens the problem.

If believers are insisting that morality is grounded in God just because it is then they show they do not believe in objective morality at all. You cannot have morality if you fill it with or base it on vicious circles. A vicious circle is an attempt to make something look proven or rational when it is not. Its a lie.
The hypocrisy
To say that morality is based on God means that you cannot take morality seriously unless there is a God to punish the sinner and to reward the saint. That would mean all you care about is the getting a prize and avoiding punishment. Only a stupid God would be pleased with a mercenary such as you! And remember if the only reward you want is his approval that is still a reward you are looking for. You want a crown for how it will make you feel so only wanting God to be pleased with you is still about the reward you want in a positive feeling.
Good is not the same as moral good
Morality is based on there being good and evil. You can be good without being morally good. A good person might give all they have to an evil person. The morally good person will consider what people deserve and give to the deserving. Morality is about what we deserve be it reward or punishment.
The good person is not necessarily the same as a morally good person. The evil person is not necessarily the same as a morally evil person.
Good is related to morality but it is not the same. Good is more important than morality. If morality is impossible you have to be good instead.
If God is good that still does not justify morality for morality is a different type of good and depends on good.

Religion says that if we say God creates all and is totally flawlessly good then evil is a problem. And it alleges that if you say evil shows there is no God you end up with a problem of how good can exist if there is no God. If the problem of good bases good on God it does not base moral good on it at all. You need another base for it. Religion says God is not a moral agent for he cannot do wrong. A moral agent must have the power to do wrong but refuse to. In fact, God being a non-moral agent shows that God has nothing to do with morality at all and cannot be used as a God of the gaps to bolster it up. The moral argument is full of immoral lies!
Good is default
If there is no God or creation or universe, it is good in the sense that there is nobody around to suffer. If there is no God or anything to make people, it is good that there are no people around to suffer. So good is independent of God. It can exist without God.
Good and morality are not the same thing. There is good up to a point in all evil actions. Morality means that some action is good overall or has more good than bad in it. Good and evil would exist even if there is no God. Thus moral good can exist without God too if moral is defined as being what is the best.
Law also exists by default. Suppose it is not objectively good to feed a baby or kill it, then it is the law that morality is nonsense. It becomes evil to say that feeding or killing it is objectively wrong. There is no logical problem with the notion that the only thing that is objectively wrong is to lay down any other objective moral judgements.
So it is objectively good to realise that there are no rules except realising that rules are meaningless. No moral laws are really moral except the rule that they are nonsense.
So no matter what you do or who you are, you are compelled to have an objective morality.
It is a default. God has nothing to do with it. He did not make the rule that 1 and 1 is 2. He cannot change that rule. It has nothing to do with him. Thus God and objective morality are not connected.
Anyone who does not see this does not understand goodness or law correctly and faith in God is holding understanding back. Faith in God is intrinsically evil for it bows to the lie that God is objective morality and the ground of it. It may feel good but proper good makes you feel even better. Not all things that are enjoyable are good.
If good can exist without God, then morality when understood as doing the most good can exist without God. And indeed it does!

The problem of good
What is the problem of good? Believers in God say that if you argue that evil contradicts the notion of an all-powerful and all-good God, you are forgetting that the problem of good is more important. They say that there is no explanation for how good can exist if there is no God to create it. They call this the problem of good. They say it is more important then the problem of evil. They say the person who says there is no such God has a bigger problem, the problem of good, than the problem of evil.
This denies that good is an assessment not a force or power or an entity. It is still good to be alive even if nobody exists and there is no God or universe or anything.
It is really a plea to dismiss the problem of evil and thus it is evil for even suggesting that. If that is what you have to do for the sake of this problem of good then its not really good.

The notion that God is the ground of objective morality certainly implies that to deny the existence of God is to create a problem of good. The problem is nonsense so God cannot be objective morality.
Instrumental or intrinsic or both?
"Good moral qualities such as kindness and compassion and being fair are not intrinsically good. They are only instrumentally good. For example, if there is nobody to be fair to in the world then it does not matter if you are unfair. Fairness is only valuable in an unfair world. Kindness and compassion is only valuable in a hard cold world. Virtues are only for a universe of hard knocks and no good in a universe that is all sweetness and light. They are no good in a Heaven."
To this I say that instrumentally good means intrinsically good. So even if there is nobody to be fair to then it does matter if you are unfair in your heart or do not care. An object is good in itself regardless of whether or not it is used. So it is with our actions.