Along with a form rejection, a bad review is up there on the list of soul- and ego-crushing things that can happen to a writer in the course of their daily working life. Patricia from http://www.epublishabook.com/ has a two part article discussing some prevention and coping strategies for bad reviews.
There are different kinds of bad reviews, and each should receive a tailor made treatment. Bad reviews can be divided according to their source or to their content.
Patricia provides a very nice, detailed breakdown of how to respond. The core message, as you should already know, is that an author should always be polite and courteous. Your image is your brand, and your public behaviour is your image.
I particularly liked how to avoid (not cope with!) criticism of your style:
Critics about the style These are best avoided by offering free sample chapters. A reader who does not like your style will simply not buy the book and have no reason to complain. If it happens nevertheless, most of the time, it is best to ignore it, or to hope that other readers will comment on that critic.
Note that doesn't help you if you've already received the bad review, but it's a healthy and supportive mitigation strategy.
Do check out the rest. You can read part 1 here: What to do with a bad review - Part 1 - Looking at the source of the review
...and part 2 here: What to do with a bad review - Part 2 - Looking at the content of the review