Satan has no need to harm humanity, just as a giant has no need to harm an ant farm. He, too, is a deity, much beyond our ways. (According to religious logic)
"Instantaneous worldwide total belief! And then -you know- eventually of course, they'll be fighting amongst themselves. Ugh! Some, claiming to believe in a more effective way than the others and a whole new Era of prideful, self assertion will be ushered in and the innocebt will be pursecuted right alsongside the guilty and nobody's gonna know whats right from wrong anymore..." Now there's something worth debating. But, wait! Lady Gaga is doing something meaningless, somewhere. Let's go!