True, but realistically the time involved with moderating every single review would be astronomic. I find that in the long run the bad reviews don't really matter, and that goes for any book. Just skimming the reviews reveals the authors are simply pushing their own agendas. Their "opinion" are easily dismissed and are usually firmly challenged in the comments. If you come here with your bias firmly cemented in place, you might be deterred from buying the book. But if that's the case, you probably would have tossed the book aside pretty quickly anyway. But the "deniers" who just regurgitate their own biases eventually get drowned out by the vast majority who actually bother to read the book. If the book is bad, that won't help. But if the book is exceptional, like GCBC, the attempt to derail the book fails miserably. I've seen this happen for quite a few books. The most recent example is the book Atkins for a New You. Campbell posted a long irrelevant negative review and got all of his zombies to post some as well. (Or most likely someone else urged them to go 'support' their guru). Which was a mistake because it makes Campbell attack on the book even more transparent. In the end it doesn't matter. The good reviews far outweigh the bad, and the book still has 4 1/2 stars.
I'm doing my best to flag posts as inappropriate that don't review the book but what basically amounts to a single chapter of the book, or a summary of the book.
When a book sets out to research the science and history of the current dietary dogma, you can't attack it for the list of questions that it asks. If you aren't happy with the quotes, the studies referenced, or the science in the book, by all means, attack that, but not the questions themselves.
The book is about how people have reacted to challenges in their rigid beliefs. To be one of those people reacting to the challenges in their rigid beliefs, you're only acting out the history and patterns described in the book, thus rendering the book correct.