It's a bit like global warming denialism. Admitting that child abuse within families is not extremely rare has absolutely horrifying implications for people's moral universes. Much easier to deny it happens.
> [Update, written a few weeks after the rest of this post: maybe it is all wizardry. I recommended this book to a severely traumatized patient of mine, who had not benefited from years of conventional treatment, and who wanted to know more about their condition. The next week the patient came in, claiming to be completely cured, and displaying behaviors consistent with this. They did not use any of the techniques in this book, but said that reading the book helped them figure out an indescribable mental motion they could take to resolve their trauma, and that after taking this mental motion their problems were gone. I’m not sure what to think of this or how much I should revise the negative opinion of this book which I formed before this event.]
"We have some treatments; they seem to work sometimes, although we don't really understand why and they're not entirely reliable" is still a far better place than "we have no treatments", which in turn is far better than "your condition does not exist and you are lying". I feel slightly better about SSC for admitting this and being willing to carry on working in an uncertain environment.