How do you arrive at absolute moral values if they are not God-given? There are some very real limits like declaring murder a good thing which will just extinct your moral values pretty quickly but besides that? What is fundamentally wrong with killing people with green eyes?
What can you provably say you know? What is irrefutably beyond dispute and based on no suppositions whatsoever?
When has a god ever demonstrably actually ever given any sort of commandments?
So where are the absolutes hmmm?
What is fundamentally "wrong" with killing people that have green eyes? I don't know. What is fundamentally wrong with killing people who don't pray like you do?
When you have to ask questions like that, I think you have not followed the issue far enough.
> How do you arrive at absolute moral values if they are not God-given?
Its just as possible to assume moral axioms directly as to assume moral axioms prefaced with "God says". You can do this either for detailed rules, or for high-level rules from which detailed rules are derived by reason.