I think I agree with behindblueI's on this one.
Also For me if I'm faced with a self defense situation then I'm not going to base my level of non lethal or lethal force on someone else's case or ruling. I will base it on the threat that I feel at the time. Notice also how I said less lethal. I think some people who carry a gun forget that just because we have the deadly force option it may no always be the best or only option. I still recommend pepper spray, keys, hand to hand training, fleeing if safely possible, ect. We never want the option to take a life to be an easy decision or the only option. It is a life long decision even if your right in using it.
Also I will take into consideration the "unarmed" persons size and also their words to me. Have they threatened my life and look like they might be able to follow through with just their hands? I'm not going to hypothetically make that choice on the Internet because it comes with serious consequences and is an in the moment decision based on what you feel and see and hear.