This begs the questions: Was "refrigerating" Barbara stupid? Was making her Oracle stupid? It's hard to call "The Killing Joke" stupid and wrong.
As Alonzo Harris says in Training Day, "There are some profoundly evil people walking these streets right now." They could have done a good story where Cassandra Cain decides that the world has "profoundly evil people" in it, and Batman's way just isn't enough. Nyssa even tried to talk her into it in a BATGIRL issue.