I think the balance of the film is firmly in favour of the strong relationship between Caractacus Potts and his children, and that children even at an early age grasp the concept of good and evil as it is portrayed in this film. Good always wins, and the Child Catcher has no redeeming features (even physical!) at all, which helps to reinforce the fantasy aspect of the story, which small children are able to understand. There is an element of subjecting ourselves to unpleasant experiences that is in-built in us all - horror films and fairground rides have been exploiting this aspect of our psychology for years now, and I think you are an exception in not enjoying CCBB, although you continued to watch it, which does underline my point.