I can understand a publisher requesting that you post a negative review after the initial release hype dies down, especially if you received an advanced copy as part of a tour. You do have a right to your opinions but I also get the publisher’s perspective. The first few weeks after a novel goes on sale are some of the most critical publicity-wise and the publisher usually puts a lot of work and money into their marketing campaign so I get that they want to focus on the positives.
I’ve never been asked to not post a review because of how I rated it but I would consider delaying it if the above circumstances applied. However, if I purchased the book with my own money then that consideration goes out the window. Once the novel is for sale, you can’t start harassing negative reviewers; it’s just bad business. It also annoys me that many authors / publishers view 3-stars as being a low rating. I’m no Math whiz but on a scale of one to five, three is average. And finally, if a new release ONLY has 5-star reviews, I’d immediately be suspicious. There’s not one book in the entire world that’s going to please everyone and negative reviews are just as important as glowing ones in my opinion. I’ve lost count of the number of times that I’ve bought a novel BECAUSE of a less than stellar review. You know what they say… there’s no such thing as bad publicity!