It’s too easy to publish a book these days. I know that for sure because I’ve seen far too many that should never have been published. I have also seen authors defending their work in the face of valid criticism and have had to deal with several such authors myself. I have suggested to several that they unpublish their book, fix it up, and then republish it, but I know of none that has done so. (The fact that I think it is worth fixing up is a very good sign.)
Some, rather than thank me for the time I took to give them detailed feedback, preferred to abuse me but, thankfully, two took my suggestions to heart. They published revised editions that solved the initial problems to the extent that they then earned a place on the Awesome Indies list. Those authors showed the right attitude. They are the ones that will grow in this climate, the ones that the indie movement is made for.
Those who get defensive, argumentative or bitter when faced with criticism, however, and who refuse to consider or appreciate well-meant suggestions should not be in this business. If you publish a book without due study, preparation and feedback from qualified/professional people, then you risk unknowingly publishing something that is substandard. When that happens, don’t complain to or about the people who point that out to those who might buy your book. The threat of bad reviews should be a moderating influence for potential authors and rightly so.
When you publish a book, anyone can read it and write their opinion in a review. Every single reader has that right, and no matter what you think of their opinion and no matter how damaging their opinion might be to your sales, negative reviews are the risk you take when you publish. That’s the rules of the publishing game, and if you don’t like the rules, don’t play the game.