I am not a book reviewer, but my husband is an artist, he also writes music and is trying to get into the children's writing industry, and we have both done a lot of theatre performing. From that point of view I would expect nothing but honesty from a reviewer! Isn't that their job?
Not everyone who sees you perform is going to agree with your acting choices. Everyone who looks at my husband's art has a different opinion. Some people love it, some people think it is weird, and there might be some people who hate it. We all have different styles and opinions. As an author, you can't expect everyone to like your book, and you shouldn't get offended when someone is doing their job by giving you their honest opinion. It is hard to get honest criticism from family and friends, because they don't want to offend you. Part of the job of being an artist, author, or performer is to take the criticism in a constructive manner. I don't think I could be a book reviewer because I hate offending people, but I would like to think that over the years I have learned how to take honest criticism. If it is given in a respectful manner it can be very helpful in improving your art form - whatever that may be.