You make very good points. It can only be hoped that the parent taught the child how to protect himself. That very well could be the case. The child would have been 10 when it began. Predators are extremely vicious in what they tell children, and how they get the child to believe what they are saying.
Regardless of how well taught someone may be (to protect themselves) there are circumstances that can negate that training, or render it useless, or ineffective.