"There's a human morality in about the same sense as there's a human language." (This is what Greene seems to believe and it's a dispute of fact.)

That seems to hit close to the mark. Human language contains all sorts of features that are more or less universal to humans due to their hardware while also being significantly determined by cultural influences. It also shares the feature that certain types of language (and 'ought' systems) are more useful in different cultures or subcultures.

This is a wonderful epigram, though it might be too optimistic. The far more pessimistic version would be

I'm not sure I follow this. Neither seem particularly pessimistic to me and I'm not sure how one could be worse than the other.