Imagine someone writing a story where, for example, Christopher Robin kills someone, and profiting from it? Would you be happy having your childhood memories of reading Winnie the Pooh tainted like that?

Interesting that you chose this example, because it has already happened in a commercially-released horror film. The result wasn’t in any way damaging to the legacy of the original work; all the books, adaptations, and such that kids love are still available. All that ended up happening was that people who like that particular sort of thing gained a new movie to watch, people who don’t like it can ignore it, and pop culture as a whole keeps chugging along undamaged. All our childhood memories of Pooh are still the same ones we had before this movie came out.