It's pretty tough to prove hatred, but bad philosophy or bad religion are much easier to prove than emotion, because they can be better expressed in words and concepts which can be weighed against themselves(for self-consistency) and various self-evident truths and, if we share the same religion, the truths of revelation.
Now if you insist that there are no self-evident, shared truths across cultural or religious divisions, I'll again cite Augustine on the justice present among pirates. Though their sense of justice is woefully limited, being the justice only necessary for their survival, even this basic kind of justice is a good that transcends merely particular group interest: nobody likes being murdered. You pirates don't kill us, we civilized folk won't kill you.
What's worst, how do YOU know that crashing planes isn't the RIGHT thing to do and it's YOUR moral perspective that is messed up?
Let's get this back to the general principle I was defending, "the direct taking of innocent human life is wrong." I would say this is true by definition: an innocent person is by definition not guilty of a punishment, and thus doesn't deserve death, an objective evil. But I think I can anticipate your objection: Why think death is an evil? Might death not be good in some cases, where you're actually doing somebody a favor by killing him and freeing him from his miserable life? Isn't all this life-affirming silliness a product of Christianity? Maybe the gnostics were right, and the body is really a prison for the soul. Mass murder is really mass liberation!
Let's say for a moment that life really is an objective evil. Even if that were the case, one cannot take away something from somebody without his permission: you don't have clear title to another man's life. (Neither does the individual have clear title to his own life, one reason why suicide is morally problematic). I could go on and try to prove that having a title to something is a part of justice, but I think I've proven what I set out to do.
These are rhetorical questions and I'm not trying to put you on the spot. I'm just trying to make a point, as the philosophers did, that if you took ten religious figures from ten different cultures (even the same culture) and asked them to compose a list of natural laws you'd get 10 different lists.
I would argue there would be considerable overlap between those lists. You'd definitely get the bare minimum "pirate justice" necessary for the maintenance of society. People who have a death wish are few, and whole cultures with a death wish have already gone extinct.
Since you've brought up the Bible, may I point out to you that,as Budsizewski noted, St. Paul talks about the natural law? See Romans 2:13-16:
For not the hearers of the law are just before God: but the doers of the law shall be justified. For when the Gentiles, who have not the law, do by nature those things that are of the law; these, having not the law, are a law to themselves. Who shew the work of the law written in their hearts, their conscience bearing witness to them: and their thoughts between themselves accusing or also defending one another In the day when God shall judge the secrets of men by Jesus Christ, according to my gospel.
Are you boiling down Natural Law into one thing-the taking of innocent human life? I had a broader scope in mind which I think you do to.
But let's assume that Natural Law ONLY encompasses the taking of human life. Your pirate analogy ("You pirates don't kill us, we civilized folk won't kill you.") indeed sounds strange coming from the pirate's perspective ("You civilized folk don't kill us, we pirates won't kill you.") The cultural differences is apparent. How do you know the "civilized" folks are much more in tune to their Natural Law then the pirate folks? Just because you happen to agree with the civilized folks doesn't mean your Natural Law self isn't skewed as well.
My point is without some clear guidance, our moral compass is skewed. The Gnostic might have been right had not God given us His word. While Moses was up on Mount Sinai and God was writing the tablets, the children of Israel (Aaron included who should have known better) was making golden calves, breaking the laws even as God was writing them-Ex 32. They didn't exhibit any Natural Law so why would you think we are any better then they and have an innate sense of Natural Law? God could have just said, "follow your conscience".
I was wondering when that verse in Romans would turn up. Indeed those:
"Who shew the work of the law written in their hearts, their conscience bearing witness to them"
This isn't about a Natural Law that mankind can and should aspire to. The law Paul talks about does not justify, it condemns.
Rom 3:19-20 "Now we know that whatever the Law says, it speaks to those who are under the Law, so that every mouth may be closed and all the world may become accountable to God; because by the works of the Law no flesh will be justified in His sight; for through the Law comes the knowledge of sin. "
It is there to condemn-to show that no matter how hard we try we CANNOT live by it. I'm afraid I would have to post most of Romans but consider:
Rom 2:20-22 a corrector of the foolish, a teacher of the immature, having in the Law the embodiment of knowledge and of the truth, you, therefore, who teach another, do you not teach yourself? You who preach that one shall not steal, do you steal? You who say that one should not commit adultery, do you commit adultery? You who abhor idols, do you rob temples?
Rom 5:20 The Law came in so that the transgression would increase; but where sin increased, grace abounded all the more,"
The law God gave us in our hearts was not one in which mankind could aspire to. It was one in which revealed our sinful self. This is not a law we can live by. If there was Natural Law Paul would say "you who preach that one shall not steal, listen to your inner self."