If you want a detail review, I have read detailed review on newspapers pinpointing all the negatives of some movies. Those reiews are harsher than a single sentence saying it is a bad movie.
I tell you an example. Since I criticised the blog of one of my facebook friends, she "unfriended" me. It was an open criticism. I don't want to make anymore enemies.
If you say there must be reasons for negative opinion, to justify the meaing of "review" I agree to that. But you can never demand it must be honest. Because you can never prove it is honest or not. This is "art".
In short, you must be ready to face any bad comments when you submit something for review. Else you do not ask for review. Disable comment option in blog.