You do make a good point. I think the emphasis on "truly an emergency life/death" situation though is the context.
Here in Missouri we do have the right to defend an innocent person under attack.
On another forum a man reported his recent experience.
He was in a parking lot and saw a man attempting to rob a woman, he yelled out at him, "Hey, stop!" and the man turned on him with a knife that had dried blood on it. He pulled his firearm and ordered the man to put the knife down, the man did, and fled.
The police found the man a few blocks away and arrested him.
Come to find out the guy had committed a number of rape/murders and his MO was to force women with their young children with them, and drive them out somewhere rape and kill them.
That's the kind of situation I think we would understand to be defending an innocent life, etc.
But your point is well taken, indeed.