Another thing... Philip Pullman accuses Lewis of sado-masochism because of the scene at the end of The Silver Chair where Caspian, Eustace and Jill go into the school grounds and give the school bullies a good seeing-to with the flat of their swords.
Obviously Mr Pullman wasn't bullied at school, otherwise he might have enjoyed this scene more. Anyone who was bullied at school would appreciate this scene. It's not so much that one would actually want to carry it out, it's just a cathartic thing to read.
Also, the Narnia books are fairy tales - i.e. a fantasy version of life, where people get their come-uppance in a fairly graphic way. As in the Brothers Grimm fairy tales (Märchen), such as the original version of Cinderella, where the Ugly Sisters cut bits off their feet in order to fit into the fur slipper (not a glass slipper) which Aschenpüttel (Cinderella) wore to the dance, and the reason they are discovered is because blood oozes out over the side of the slipper. (The Grimm version was bowdlerised by Perrault, the French author who popularised the story. These are psychological symbols, not actual events (see Bruno Bettelheim's excellent The Uses of Enchantment for more examples).
As it happens, I think CS Lewis did confess in one of his more candid moments to SM leanings, but I think he would have been reasonably careful to keep them out of his writings for children.