Perhaps I'm a little jaded, but after fifteen years in online bookselling, I've learnt that defensive difficult customers are never, ever worth it. Ever. Some people wish to equate difficult with discerning, but although discerning customers can be difficult, they always show you the money before they start being difficult, but that aside.

To me 'did you even read it' is hyper-defensive, and I would have ignored the email and saved myself the elevated blood pressure of dealing with what followed.

I think it's quite amazing the time you spent explaining your work to him, but in my sad experience, this sort of effort is wasted on these people.

One might hope that eventually this guy gets some sense thwacked into him, but while he's at the defensive stage, I don't think he is reasy to learn anything.