When evaluating a buy, often you see a section at the top of the screen about seeing a review of the item previously bought by someone else. Once you click on the reviews, you see what someone else has to say about the item you are considering. It could be a movie(dvd, vidio) or many other items. What you are viewing is what someone else has taken the time to pass along after they have had the opportunity to evaluate it. It could describe what was perceived to be a really good value, something that was especially disappointing in terms of expectations or conditions, etc.
This is what someone wants to tell others about, whether it positive or negative. You have an opportunity to evaluate the review, that is to say, if you thought it to be of any value to you. Was it helpfull; did it provide insight that you would not have had. Did it make a difference in whether or not you made the purchase of the item being reviewed or not. It is not about whether you like what the reviewer had to say about it. If the review was negative, it doesn't mean that the reviewer made a poor review; it means that the product was, in their opion, not as good as they thought. Don't shoot the messenger. Certainly, if people indicate that the review wasn't helpfull, when they really meant that they didn' like what the reviewer had to say, it will be a self defeating process. People just will not take the time to provide any reviews.
If you don't like the review because it doesn't provide any insight, fine. But don't shoot the messenger.