There's an old saying "Dog bites man isn't news, but Man bites dog, that's news." An author railing against libraries, that's a Man bites dog story.
The Wikipedia article also says this.
Terry Deary has said of historians: "They are nearly as seedy and devious as politicians..They pick on a particular angle and select the facts to prove their case and make a name for themselves... They don’t write objective history... Eventually you can see through them all. They all come with a twist."
He writes history too. And his histories aren't objective either. He's taking an angle, selecting facts and giving it his own twist. I haven't seen any of his books, but I've seen videos based on them. They are interesting perspectives, but not the whole story either. And his rants against libraries aren't exactly historically objective either. It wouldn't stop me from getting his books (which I might to at the bookstore or library), but it doesn't mean that I'm going to take his rants seriously.