There's nothing to explain, the pedophilia is gratuitous. You can't explain that to average, below average or above average people.
How do you know it is gratuitous? Have you read the book?
I haven't, and know nothing of it, except that the book itself is still in stock on amazon.com, so it's not out-of-print or something he's tried to hide.
Interseting to see how this plays out. Did any of the critics who reviewed this book when it came out make any mention of these passages?