What IS good, and how do we determine it?

[Metis]

I agree. But they are dangerous because they believe horrible things (rape, murder, etc) are moral. This does not apply to Randy.

Actually the Salafists (what ISIS are) are against rape and murder, but they make a separation between "just" and "deserved" (Salafists deserve protection but everyone else is just cattle to be used as wished). It's rather akin to the Catholic doctrine of Just war; killing is bad, but some people like heretics should be killed as well.

The 10 commandments are pretty explicit about "Thou Shalt Not Kill", but the Catholic Church does not condemn Capital Punishment. Francis may personally complain about it but you may have noticed he does not forbid it.

If it was that much of a slippery slope, don't you think many more Christians and Jews would have the belief that God wanted them to rape?

I think most Western Christians and Jews are too busy wrapped up in their white picket fence subpurgatory to really muster up the fervor for a Crusade. If you look to South Africa where the religious passion runs hotter "corrective rape" against women, especially lesbians, is actually a thing in Christian groups.

You've also got some Hasidic Jews over in Israel who think the new Israeli state needs to be destroyed and the "westernized" women who aren't subservient to men all need to be put to death. After a corrective rape of course, although what they're trying to correct if they need to die anyway I don't know.