Good points. I often think that Islamists know, inherently, innately, that blowing up innocent men, women and childrens in skyscrapers, pizza parlors and crosstown buses is WRONG, is the breaking of a Universal Natural Law...but they have chosen to suppress their conscience in favor of their man-made cultural command to kill in the name of jihad.
Yes, it can be a fine line to determine what is a God-given instinct and what is man-made.
Having lived among that culture for a while I would disagree. As difficult as it is from our cultural perspective, there are people (not all) who have no qualms about the taking of human life especially if there is great hatred-not only in Islam but here in the United States. But do these people feel ANY type of moral conscience that is just surpressed? If so it is so far surpress that it isn't showing even to them. They're just serial killers who kill and want to kill again.
If everybody's value system was somewhat consistent then natural law could possibly be argued. Unfortunately, people's value systems are NOT consistent. Different cultures have different rights and wrongs from which their laws are based. Consider Sodom:
Gen 19:9 But they said: Get thee back thither. And again: Thou camest in, said they, as a stranger, was it to be a judge? therefore we will afflict thee more than them. And they pressed very violently upon Lot: and they were even at the point of breaking open the doors.
They didn't like anyone telling them what to do. They looked at Lot as being judgmental. For us to say that, "Oh, they really KNEW what they were doing was wrong but it was just surpress." is kind of crazy in my mind. There was no talk about considering Lot's proposal. They knew precisely what they were doing.
The more I think about natural law, the less I agree with the concept.