In your position, I would validate their viewpoints and then counter. "You may feel the book was poorly written, but I don't think that's what's important. What is important is what it tells us about the character, the author and ourselves. The book was written the way it was for a reason. I ask, would it be the same book; would it get its point across as well as it does if it had been written differently?"
Show them some NF compassion and understanding. Throw 'em for a loop