The backing is the existence of objective moral values that we all recognize and adhere to and believe in.
What moral values are these that we
all recognise and how do you know that they are objective?
Moral values that we all live by and expect others to live by. If objective moral values exist that are based outside of ourselves as opposed to subjective morals which depend on us, our situation, our culture, and our preferences, then it logically follows that theism is the more plausible worldview than atheism.
No it does not. This is unargued. How is it that a framework for objective morals somehow necessitates theism?
The reason for this deduction is that atheism provides no allowance for these values. Subjective morals change, can become contradictory, and might differ from person to person. Objective moral values do not.
Is something objectively wrong (say, murder) according to reason according to you?
Think about it, in atheism, there is no moral right and wrong. There is no moral "should and shouldn't”. Why? Because when you remove God, you remove the standard by which objective moral truth is established. In atheism morality is up for grabs.
Atheism is not a deciding factor on my morality. Atheism dictates nothing in my life. It is in fact, a consequence of my other opinions (humanism, rationalism, empiricism) that lead me to atheism - not the over way around.
The values expressed such as: do not lie, do not steal, do not commit adultery, do not bear false witness, etc are binding upon all and they don’t change depending on your opinion, your situation, or your personal preferences.
Actually, "do not bear false witness" or "do not lie"
does change upon your situation and personal preferences. If someone is in a situation where deception would save their life or better the lives of others then that is a valid circumstance to deceive. If someone is in a situation where they are asked about something private they'd rather not share, that is a valid circumstance to deceive.
Committing theft if needed for survival of yourself or your family can be morally justified. Committing adultery is generally a douchey thing to do. I can think of no circumstance off the top of my head to justify that.
Therefore it is always wrong to lie, to steal, to commit adultery, to rape, to murder etc. Under the atheistic view, morality is formed in a subjective manner, i.e "whats good for you might not be good for me", or "what is wrong for you might not be wrong for me" etc.
You betray an understanding of morality that appears to conflate it solely in self-interest. If someone says "whats good for you might not be good for me" or "what is wrong for you might not be wrong for me" they're only talking about their own objectives. They're not considering the implications to others, which to me seems the very essence of morality. Disregard the concern for others in morality and you are left with a rather obnoxious and sanctimonious form of self-interest.
If one were to take this ideology at face value and follow it to its logical conclusion, you would be witness to what Friedrich Nietzsche speaks of when he says:
"When one gives up the Christian faith, one pulls the right to Christian morality out from under one's feet. This morality is by no means self-evident. Christianity is a system, a whole view of things thought out together. By breaking one main concept out of it, the faith in God, one breaks the whole. It stands or falls with faith in God."
Condemning murder, rape, genocide, adultery, deception, theft etc are not bound by Christianity. It is trivial to condemn them outside of Christianity and for non-christian reasons.