According to your logic the four year old toddler who takes daddy's gun from the top of the night stand and shoots his little sister in the head is the one to blame.
Pappaj, that is some brilliant logic you posit and I'm sure most everyone will agree with you. Who wouldn't blame a four year old if their parent was that irresponsible? That obviously equates to an adult stealing a firearm from a unlocked or locked home or vehicle and shooting someone. PS-What in the world are you smoking?