That is a good observation. The humans that perpetrate these terrible acts against other human beings are/were simply murderous animals and societal misfits to begin with. They simply discovered a place at some point in their lives, that would "allow" them act out their anti social doings under the protection of religion.
Ah, good ol' religion, a convenient cover for all shapes and sizes of bad people.
Hey, and if you're not religious before you commit your bad deeds, you can always conveniently convert to the religion of your choosing to minimize in the eyes of your peers anyway, the bad things you've done.
God has been asleep at the switch I'm afraid.