No worries. I'm grateful for your thought-provoking and well-written comments.

I'll just add for the record that while a society in which everyone is free to murder anyone else wouldn't really be a society, the strategy that's been successful throughout the animal kingdom (and in most human societies) is that the elites at the top of the dominance hierarchy are empowered to act villainously with impunity, while morality is reserved for the underlings as a means of maintaining their submission.

Also, if moral behaviour is consistent with game theory, that might be because game theory and the just-so stories of evolutionary psychology are unfalsifiable and tautological. (See the Stanford Encyclopedia article which points out that "utility" is often interdefined with other fundamental game theoretic concepts to be tautological.)