I highly recommend never responding to critical comments (in reviews, blog posts, comment threads, etc.) online. I have done so a handful of times and regretted it every time. You are very unlikely to be able to respond to criticism in a constructive way in the heat of the online moment, and once the moment has passed you will realized it is faintly ridiculous to respond to things that were written after half a moment’s thought and most likely not even based on the slightest serious engagement with what you have written. You’ve had the great privilege of being able to spend a great deal of time shaping and polishing your ideas, then interacting with editors and early readers to refine them further. Why throw that all away with a hastily (and probably angrily/nervously/defensively/imprudently) composed reply? And furthermore, a hastily composed reply that, unlike your carefully written book, will be instantly accessible via a Google search for your name for ever and ever?
(Equally good advice, which no one including me will ever take: “What Absolutely Does Not Matter and Should Be Ignored If At All Possible is the Amazon rank of your book. It means nothing…I recommend never checking it.”)