Oh bloody hell, this is terrible. When will people grow up? A review is one person's opinion - and they are entitled to it. How can anyone write honest reviews if this is the consequence?
Writers who send in their books to be reviewed can blame no one but themselves if what they have written and had published isn't up to standard. Either man-up and accept what someone's opinion of your book is or stop hawking it around in the wild hope of getting a sycophantic and probably unrealistic review. Everyone is entitled to their opinion. It's a disgrace that an author either encourages or fails to curb the activities of their so-called fans in having a vendetta against any reviewer.