I think the obvious question is that we did what we did not becuase we “interpeted” our religoun to mandate that.
We did it becuase at the very time G-d “personally. told our leader’s to do that. And since3 we were told to do it directly by G-d we did it , even though it went against our personal feeling’s of pity.
This is evidenced by the fact that year’s later Shaul HaMelech did display trait’s of mercy shouwin his personal discomfort with following the directives of SHmuel HaNavi and lost his crown becuase of it.
They (ISIS) do what they do becuase they enjoy killing, they are intrinsic murderer’s so they decide that g-d wants them to do it.
We abhor killing, and kill only when G-d tells us to, not when we decide he wants us to.