But that's just the point I'm trying to get across. If your fundamental motivation for a specific killing is "protect myself" or "protect these innocents", then it is that desire, that motive, which should be reinforced.
That's your
conscious motivation, not the
fundamental part of who you are. If you're a wizard, you can probably find out a way to protect yourself or someone else without killing using your magic.
Remember, magic isn't all about conscious, deliberate thought--it's emotion, it's your soul.
Deciding, consciously, that you have to kill someone is a different thing than
believing in your heart and soul that you're right to take someone's life.
You're effectively turning your own being, your own soul, into a murder weapon when you kill with magic. You can clean blood off a sword. Cleaning it off your soul's a little harder.
Basically, when you use magic to kill, what you're reinforcing is your belief that you can decide who to kill--and the more you believe you can decide who to kill, the more likely you are to see killing as a solution to problems, because that power over life and death is a rush and feels good. It becomes a mental addiction. Everything starts to look like a nail, and you're holding a really big hammer.