As an atheist, because you don’t use “religion” as your moral guide, do you consider yourself a moral relativist, or do you believe in absolute morality? In other words, do you believe that cultures, or even individuals, can define their own rules on what is moral and what is not “as long as they are not hurting anyone”, or do you believe that every action has one unique, absolute, and true moral assessment?
If you believe in moral relativism (you do not judge other people’s actions or cultures because their moral code is different than your own, mostly because it is accepted practice today), then you must necessarily also not use the morality argument as a reason to be an atheist – simply because the morality of the Holy Scriptures was practiced by a differnt culture, or because you don’t believe the Scriptures to be true, does not mean it can be judged.
If you believe in absolute morality, who or what determines which actions are moral and which are not? How do you trust any human being, no matter how smart they are, to prescribe what is moral and what is not. How can you be sure that what you do today will not be immoral 10 years from now?