Mainstream Christian sects have advocated whipping yourself as penance. Islam, we all know the part about the virgins
Others advocate starving yourself or enduring physical pain to reach nirvana, so it is not simply western religions either.
All religions have some form of self-harm within them, whether currently mainstream or not. Simply part of such a very strong belief, IMO. Hell, ideologies are subject to much the same thing, for the same reasons. And remember, the drowned go willingly. Generally.
Yeah, but for most of these religions it was isolated to only extremist factions; for instance the al qaeda branch of islam. Or their beliefs were abandoned as people realized it wasn't a giant glowing being that was telling them to hurt themselves.
"It never crossed my mind to protest as we came to the pool and she pushed me into the water. I felt something grabbing my arms and legs and pulling me down, but the priestess smiled at me, and her happiness was all that I cared for. I opened my mouth to sing a song of praise for her, and it was only then that I realized I was underwater, water filling my mouth and my lungs. For a brief moment, panic filled me and broke the spell - I screamed, and the priestess threw back her head and laughed.
For a moment, I thought I felt a distant memory when I crushed the skull of the first people the priestess told me to slay. She must have seen my confusion, for she laughed in her angelic voice. With a happy gleam in her eye, she told me that the corpses at my feet were those of my wife and children. I looked at her and the bodies, and there was another momentary feeling of recalling something, but the words bore no meaning to me. I looked at the corpses and shrugged, and we left, her joy echoing in my ears."
The Overlords' also use mind magic to force their followers and complete strangers to obey them. Neutrality implies neither good or evil, but forcing someone to kill their own familiy is decidedly evil, I mean if anything they are more of a chaotic evil religion.