This misses the crucial question: Whose books were burnt? If this guy bought a copy of Harry Potter and then burned it, that's just a somewhat over-the-top way

This misses the crucial question: Whose books were burnt? If this guy bought a copy of Harry Potter and then burned it, that's just a somewhat over-the-top way of saying he doesn't like the book. Which is an opinion he's completely free to have. The problem with book burning comes when people (or the state) burns books owned by people who don't want them burned.