The elements of harmony did not posses emotions, despite what many thought. They were simply a weapon to be used against evil and disharmony, they were black and white when it came to their use. They cared not for what lead one to evil or why. When used they reflected the users desire and were open to interpretation to what the users wished for them to do. In her desire to destroy the evil that corrupted her sister. Celestia did not realize the elements would interpret it as a desire to kill!
Thanks to everyone that looked over the story. You guys rock.