Why do we enforce "Thy shalt not murder?" Seems to me that someone is forcing there religion on us here. Even in the animal kingdom, animals fight in defense of self, family and herd. Similarly human history finds humans defending self, family and tribe. It is a natural instinct. It has nothing to do with religious beliefs.
I got news for you friend. There is also a natural instinct to acknowledge and worship God. And for those who reject Him, there is strong warning, "you are without excuse."