I should really clarify this to say, “Never engage a reviewer.” Or perhaps, “Never tell a reviewer how to review.” Or how about, “Never threaten a reviewer”?
An author can do herself everlasting damage when she reads a review and decides to tell the reviewer he’s wrong. Or a troll. Or a bully. Or an idiot. Or not qualified to review because he didn’t finish the book.
There are two reasons a person will review a book: first, to talk about why he liked it, what he liked about it, and why others might like it; or second, to tell why he did not like it, what was wrong with it, and why others should avoid it.
Neither of these two reasons benefits the reviewer in any way. He doesn’t get his money back if he doesn’t like the book or if it’s poorly written, and he doesn’t get a bonus free book if he likes the book and recommends it to others. In fact, the reviewer has PAID for the privilege of reading the book, so he has the right to say whatever he darn well pleases about the book, good or bad. He has spent hours of his life reading the book and has earned the right to review it in any way he chooses, whether it be a lengthy discussion on plot and technicalities, or a pictogram made up entirely of smiley faces.