They have spread the word about the fledgling wizard Harry Potter. Their protests against the Harry Potter books are sparked by their objections to sorcery, the magic arts, wizards, warlocks and witches. They have forgotten what it is like to be a child.
All children believe in magic.
It's a way to explain the world. It's a way to have some power over the world around them. It's a way to overcome the fears children have. Fantasies and fairy tales and stories about magical powers are important to the development of a healthy psychological state. A rich fantasy life invigorates the imagination.