You would know more about this than me but are you sure? I thought in some states the response has to be proportionate. Also in many states you must try to retreat before using deadly force.
In all states the response has to be proportionate. That is, you are only allowed to use deadly force in any state if it is necessary to save yourself from grievous bodily harm.
That doesn't--and couldn't--mean you aren't allowed to overpower him. If he is going to stab you with a knife and the only way to stop him is to shoot a bazooka at him, then you can. But if you had time to warn him to stop or you'll shoot and you don't, then it is murder. Note how a bazooka and a knife are not proportionate in the "criticize Israel" sense, but are proportionate in that it is something that was necessary for you to do.
The only issue is the stand your ground, and that doesn't actually change the standard I articulated above. The deadly force you are using still has to necessary to stop him. The only difference is whether you also have to be unable to run away. I'm not exactly sure how that works, since presumably at some point it is too late to run away, and that is presumably the point you'd be using your force anyway. But stand your ground wasn't at issue in this case--nobody thinks Zimmerman was able to run away at the point in the story that we are concerned with.
So the standard you are espousing actually already is the standard in every state, with the only question being whether running away has to not be an option. And in most states and the common law, you already don't have to run away if it is inside your own house (the castle doctrine).
Aside: Stand your ground laws were passed by about half or so of the states some time ago, after some backlash over juries who were convicting people of murder in self-defense situations on the theory they could have run away. The popular concern at the time was that it is too easy to second guess what a person should do when they are under a deadly attack, and that on a doubt we should side with the original victim. It isn't just this "macho" "wild west" inspired law.