A flag represents the state, religious text book represents the teachings of a religion, a pride flag represents the minorities.

Going out of your way to burn the book of a religious group in front of its gathering sites is obnoxious and counterproductive at best, and surely one could hold actual hatred along otherwise protected expression, but the religion itself and its teachings are not above criticism. As crude as burning a book may be, you're inserting a lot of meaning in to it that just isn't actually there.