The only time I take issue with a review is when it says that a film is made just to make money or something like that. Good solid criticism is fine.
Though another thing you pointed out is how fanboys use RT to validate their love for a CBM. Heck, one of my film professors was using an AFI list to "prove" that a movie was good. He was screening
2001: A Space Odyssey and said, "even if you don't like the movie, it made it on this list and therefore it is a good film." While I agree the film is fantastic, that was a terrible argument on his part. I expected better from a Professor.