No, by definition “moral” presupposes a normative standard. That’s simple logic. It is the exact opposite of “opinion”. Now please tell me where this standard comes from if there is no God. Don’t dodge the question.
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The discussion below uses the term ‘moral authority’. It starts off saying it ‘might/could’ come from a God (God). But in the end I think it says that we, society, defines moral authority. Not laws mind you but doing what is right.
http://theblog.philosophytalk.org/2007/07/where-does-mora.html
But that definition will change from society to society and within a society over time. There is nothing fixed and it is completely relative and arbitrary. Thus, there is no objective reason why I as an individual should follow or accept what any society arbitrarily choses to define as right or wrong other than the fear of punishment.