Again, I wonder whether you're overgeneralising here. Certainly, honour killings, for instance, are still acceptable in many parts of the world still largely untouched by Western democracy, itself influenced for centuries by institutionalised Christianity. I'd be interested in what you think of your morality in connection to Islamic sharia, or African tribal law, or East Asian semi feudalism, or for that matter any number of ancient cultures now passed. Again, I completely agree that most cultures share the idea of moralistic value. But exactly what activities are morally valuable can differ markedly. I would also argue that the prevealence of our 'morality', and our higher standards of living, has much more to do with technological advance and cultural and physical hegemony, than it does a more realised and authentic morality.
Whether or not cultures have attitudes towards illegal killings is hardly surprising. If I were to put on my Foucault glasses, I would say that the power to give or take life is one of the most strident demonstrations of power available to mankind. Therefore, it is not surprising that every culture has rules about killing. What differs MARKEDLY is what is considered a legal killing. Who benefits? Is it the powerful? Is that a morality you would agree with? Why or why not?
If I were to be in the position of ultimate power, as numerous despots have been over the last couple of centuries, what is the moral prerogative to stop me or remove me from that position? Why appeal to a higher moral authority at all? Surely as long as I am able to hold sway, there's no particular moral yay or nay to prevent that? What particular compassion am I required to have towards others, if ultimately my reasons for safeguarding moral order are about my own well being? Is all that matters ultimately strength of arms, and the ability to wield superior force? Why or why not?
I would prefer a law in which the widow, orphan and foreigner are protected, myself. But I do so because my God has treated me in such a way, and calls me to do so as a result. Not particular because of what I prefer, or because of what will safeguard for me a safer society. Certainly, I live in a 'safer society', but my society exists at the expense of others, so its not entirely win win.