@atlanta
"Do they Really Really think these atrocities will turn the world towards their kind of religion ? I know it is worse than anyone's worst nightmares, but surely that has to be their perverted motivation ?"
I can't help but get the impression they want to make it so repellant that, if forced to convert at swordpoint, so to speak, we'd all happily choose death.
I know I would.
It's the way they will clean their conscience of all the killing they'd have to do, as it's all there in the book. The perverted motivation can only be guessed at, other than the basic human desire to change your surroundings to the way you want it.
Or, as psybbo put it, they are just homicidal psychopaths.