GD said it best (of course
). The idea that "person A shot person B" is always the exact same crime and deserves the exact same punishment is absurd.
What if:
A = 4 year old with daddy's gun?
A = A senile 101 year old man?
A = A person who's killed before?
OR
B = A visibly pregnant woman?
B = A person who is pointing a gun at A?
Give me a break.
Another point that I would make is that statements in black and white look lovely on paper, but that human brains do not work that way. "Motive doesn't matter" just doesn't make sense in the world of human experience, as the already-in-place legal system bears out.
I'm reminded of the "is it ok to steal medicine to make your loved one well" test they give children and teens to show that there is a gray area in good/bad and punishment that people grow to understand as they mature.