The review of Freedom of Mind linked on the page was interesting. I recently read the book so it was fresh to me. My opinion is that Hassan is a mixed bag, but mainly good.
Some of the criticisms of his book are just petty. The claim of plagiarism is unfounded. Hassan may not use academic footnotes and bibliography, but he is more than clear about using Lifton's ideas and others.
The criticisn that he uses the discredited term "mind control" instead of the legal term "undue influence" is plain weird. Because Hassan himself acknowledges in the book that "undue influence" is the better term and he has now started using it instead.
The observation that Hassan's focus is on families helping cult victims is spot on. His book is no help whatever to people in cults who don't have families that want to help them out. The book offers little hope for such people, but it never pretended it did.
The reviewer is probably correct that Hassan exaggerates the growth of cults today and it's true he offers no proof for such assertions. And yes he probably casts his net as widely as possible to make his book relevant to as many people as possible because he wants sales. So what?
I find the accusation that Hassan uses hypnosis and NLP to be obnoxious because he acknowledges that he used them in the past, was concerned about them ethically, and has now condemned both. His statements on this are quite clear and the review obscures rather than explains Hassan's stance on this.
The question of authority and legitimacy is interesting and difficult. The reviewer raises relevant questions about Hassan never being used as an expert witness and about qualifications. Many would say that Hassan's status as expert derives from his experience leaving a cult and many years helping others to do the same. He also has relevant academic qualifications in counselling I don't think are disputed.
I broadly agree with the criticism of Hassan's use of the term "cult personality" as opposed to real or authentic personality. Some people may find this way of viewing things helpful to some extent. Personally I don't. The reviewer says these descriptions have no "scientific" basis. What they mean is that it's not standard terminology in the discourse. Fair enough, but if you want to get into the scientific basis of psychological discourse in general that's a whole other can of worms.
Frankly the least interesting accusation against him I find are his prices. I can not envisage me ever paying for his services or anything like them. But what he charges is between him and his clients. If he charges too much then don't buy, simple as that. Watch a YouTube video instead.
He seems to me like a genuinely nice guy who wants to help other people. He also makes apparently a good living from offering his advice and guidance to people with a lot of money. Too much for some people's taste, but no one is forcing them to buy. Good luck to him.