I have to say I don't get the ranting. Yes, targetting parents is slightly strange, but they are the people who end up paying. It's like targetting children's toys at parents. Maybe a bit weird, but sort of understandable.
But the main thing I don't get is the passion against them. They provide a service some people find useful for a rather large fee. Is it too expensive? Probably. But then I think private schools are too expensive. Yes, a lot of the information they give is available elsewhere, but the personal service isn't (at least, not for free), which is where the real benefit is. Also, bringing all the information together in one place, just the relevant bits for that person's application, saves a lot of hassle searching and finding it all yourself.
I can understand why people think it's not worth the money, especially with the conference things. But that doesn't stop it being useful for some people - everyone I know who's used the personal service bits (mentoring, application form drafting, etc.) found it helpful.
So why are people so passionately against it? All it is is a service that they charge a fee for, like a private school, outside tuition, private healthcare, etc.