I think you should just move on, they have asked you opinion and if they don't like it tough. I have had mixed reviews from people about my book and I just take it on the chin and move on. Most of the time if it is constructive I will try and work that into my future writing.
If they get really annoyed just cut off communication and don't get pulled into a slagging match.Its not good for anyone.
Just my 2p worth.
A review is your opinion. You can state this somewhere on your site, as many reviewers do, but to any reasonable human being, it is understood implicitly. Authors should not respond to you with anything other than a thank you, and I say that as an author who has been unhappy with reviews. I remember one, a few years back, that made me wonder if the reviewer had even read the book, and do you know what I did? I fumed about it to my husband and a close friend, and otherwise ignored its existence. It is human to be upset by a bad review, but completely unprofessional to respond to one.
For your part, I don't think you should handle them at all. Ignore them. And maybe don't ever read anything by them again. :)
It's not often I get a negative review of my books, but when I do, I thank them for commenting and I review their critique and decide whether it's something I need to focus on. If it is, I will try to work on the problem, but if someone is just being nasty about it, then I say, whatever and move on. I never get angry with reviews.
In fact, reviews help us to grow as authors. Everyone is not going to like what you write or your choice of style of writing, and that's ok. I believe critiques are a good thing and I welcome them good or bad. But what I find interesting is, when I find myself in that situation, I already know what was right or wrong with my writing, long before someone tells me. I am my own worst critic. Trust me, no one can critique me more than I do myself. I'm a firm believer in fine-tuning my craft.
Each book I write, I make sure to remember what was wrong with the manuscript and I make it better. I get better and better, and that's what it's all about.
As an author & review coordinator/editor for The Pagan & The Pen Book Reviews, I see this subject from both sides. As an author, I've had good and bad reviews but I am an acquired taste and not everyone gets or likes what I write. No big deal, because the ones who do get me are fans for life. That's why there are so many authors out there - there's something for everyone.
On the other hand, as a review editor (and former reviewer) I have worked to make The Pagan & The Pen Book Reviews a cut above other reviews. First, we don't give a book a low score because we don't like the cover art, or the editing is bad. I have designed a review system that reviews 5 different areas of the book, and then we average out the scores for an overall score. I found that often an otherwise great story, is terribly edited, or has some other flaw that pulls the reader from the story. Sometimes that flaw is beyond the author's control, yet it is the author who gets the flack.
Yes, the author is ultimately responsible for his or her final product, but with publishers we often find ourselves at the mercy of their editors, cover artists, and an EIC who has a my way or no way policy.
As an author I don't think reviews make that much of a difference in the long run. I take reviews as a necessary part of my life, but certainly don't let them ruin my day or decide my future as an author.
I received a (detailed) one-star review for a copy of my book that I'd given away in a Goodreads contest.
If I could handle it (and I did), any author I review should be able to cope too.
As a reviewer, authors that request me to review receive a copy of their review before i post anywhere. I always inform them that if they feel a statement is unfair, i'm open to hearing their point. That dialogue (darn, no spell check) is beneficial for both parties. If a reviewer does contact me about a review that was not requested of me I take the time to explain why my opinion is of such, after that you either agree and re-word your statement or you stand by your opinion. Then its time to move on!!