Once exposed to EVIL and unremitting DARK SIDE antics changes people. Most despise revile abhor it and find it to be promulgated byTHE DEVIL's representative(s). Others couldn't resist it and are ensnared by it and worship it and pray to it.
The tainted don't remember whom they used to be before the dark side got them. They go out to preach the word to any and all who will listen to them. Stockholm syndrome. They are now in love with the monstrous thing that corrupted them. And so it goes.