I'm not going to quote this time because I'm too lazy to go back and do it. Just because a handgun can be deadlier, doesn't mean it isn't already deadly to begin with. I'm saying one shot CAN kill a person, but a typical handgun would have several rounds in it. If you shoot a person 5 times, will they live? Maybe, maybe not. The chances drastically fall when you put more holes in your target. They die from more than just being shot in the head or the heart.
Also, it doesn't matter if the old man was showing what he "could do" and not everything, or that it doesn't exactly represent a real life situation. The thing is that you trying to find all these flaws in the self-defense with martial arts can also be applied to having a handgun. You have a handgun, they have a handgun. Do you always have a handgun with you? If yes, will you have a handgun out before they do? If yes, will you shoot them? Most likely. Will they die? Who knows, if you're in a situation where you REALLY need one, leaving them there will most likely get them killed if you tried "stopping" them because this person may have little they can do to get help. The old man showed many situations, though, where you can overwhelm a person bigger than yourself. Not every person you go against will also be skilled in the martial arts, but if they are maybe you are screwed. However, if you have a gun against a sharpshooter, will you survive? You probably will die no matter what you have on you.
