As a reviewer I will always try to be fair in my critiques but what I write is still personal opinion. I can say what aspects of a book I enjoyed or disliked but these are feelings: enjoyment, dislike. They are a reaction that I have had to the prose, coming to it armed with the baggage of my own unique life experiences.
Part of this baggage is a strong antipathy towards sex scenes. Digressions into sex are too often voyeuristic rather than key to plot development. If sex does drive a character’s actions then I would see that is a weakness which could be more effectively portrayed by suggestion rather than detail.
In films I am turned off by those soft lit, naked romps where sheets are artfully twisted to hide male body parts whilst showing female curves being slowly caressed. I watch awkwardly and wish we could get on with the story. Don’t get me wrong, when Mr Darcy emerged from the lake in his wet shirt and encountered Lizzie in the BBC adaptation of Pride and Prejudice I was as taken by this portrayal of a new, more gentle aspect of his character as the next woman (and some men of course). I still regret that the series ended with a public kiss. Even at a wedding such behaviour struck me as inappropriate for the characters depicted.
In my own writing I have been criticised for rarely describing the outward appearance of my protagonists preferring to allow the reader to form their own mental image. I view how a character acts as more important than how they look. When I am reading a book I do not wish one character to be linked to another because of satisfying sex but rather because they make each other laugh, or admire each other’s talents or intellects. I want them to be interesting people rather than sex toys.
If one character is drawn to another by outward beauty the attraction is shallow, if by sex it is selfish. I realise that I am bringing my real life prejudices into my book preferences, but I struggle to get behind or empathise with a ‘good’ character when they display what I see as feeble tendencies.
Since the runaway success of Fifty Shades of Grey (which I have not read) it has become obvious that there are plenty of people who enjoy reading about sex. I therefore face a quandary each time I am turned off a book by a sex scene. I do not wish to decry the tale because of a personal dislike that others may not share, yet what is the point of a review if it is not honest?
Book reviews are written as an aid for other readers. To be useful, I cannot allow my personal prejudices to entirely colour my judgement. It is important to step back, to look critically at the quality and style of writing, coherence of character development and plot, at how compelling the story is. Once all of these have been considered though it is generally expected that a personal view will be shared. Perhaps I need to include a caveat when reviewing certain books. Perhaps that is what this is.
neverimitate 
People write sex scenes just for the sake of writing sex scenes. People just like reading about sex. Now, if the sex scene is completely removed from the reality of the plot (they take a break for sex in the middle of a battle, they literally hate each other but have sex for no reason) then I say criticize it, but otherwise, the best thing you could do when making a review is say “I don’t enjoy sex scenes” and then don’t count such scenes against the book if they more or less fit with everything else. (I don’t know if this comment comes across as antagonistic or not, it’s not meant to be.)
Undoubtedly some people enjoy reading about sex. I don’t have a problem with that nor with writers obliging. Literature would be much more boring if all readers enjoyed the same types of writing. I agree that if I am going to mark a book down for including certain details then I need to give reasons. That holds for any criticism. Whether or not sex scenes are absolutely necessary rather than providing titillation (which some readers enjoy) is perhaps more debatable. That writers write what they choose is an interesting point to add though. One of the challenges of reviewing is balancing the academic and emotive responses to a book. Most of us read books in the hope of deriving pleasure from the pursuit. Pleasure stimulants are very individual. Your comment does not come across as antagonistic. Thank you for taking the time to feed back.
[…] A romantic plot thread can be written with depth, humour and originality without descending into lengthy detail. As ‘Pride and Prejudice’ demonstrates, suggestion can be a powerful device. My antipathy is not towards the background to a mutual attraction but towards the reason for the intimacy and the way it is described. I have written of my dislike of gratuitous detail before, here. […]