No, I don't think this is doing a disservice to the author and here's my reason.
There are lots of books out there to choose from and very little time. Why waste my time on a book that doesn't capture me? Why bother writing a bad review when it may just not be my cup of tea whereas it's exactly what someone else may love. I would hate for them to not read the book just because I didn't like it. Everyone has their own taste in books. Who am I to say a book sucked? You might love it.
It's all in perception.
After I write my reviews I love to check to see what other people have said about the book I just read. Unfortunately, some people just don't know how to write a review that says they didn't like it. Instead I've found that some people are just down right obnoxious and rude. I read one review where the reviewer litterally attacked the author for being stupid. The reviewer didn't like the world the author created. She went on to say what she would have done. I checked this particular reviewer's main page to find that she is a writer herself, a self-published author.
Now, I don't have anything against self-published books. Some of them are absolutely astoundingly wonderful. I have noticed, however, that some self-published authors feel they are superior to authors who have gone the traditionally published route. The same can be said for traditionally published authors looking down on self-published authors. I don't think either side can truly tout their superiority. There are great authors on both sides. I've also read books by authors traditionally published that I didn't like much.
My take on this was that the reviewer, being an author herself, acted unprofessionally. She didn't like it, that's fine. Just don't attack the author's ability to write. The book in question was well written. I never found a mistake, so the editor did his/her job well.
This particular review wasn't the only bad review out there that attacked an author. I found at least two of these types of reviews on each and every book I read during my hiatus. I was astounded by the number of people who have no problem attacking others viciously through reviews. It made me angry at the reviewer for the attack and sorry for the author for having to read it, ever.
Your Turn -> Do you think that it's professional for authors to write negative book reviews that attack other authors?