I've done quite a bit of shooting. And I agree that it's not easy to aim with a handgun (I don't know if that includes rifles or not, but I mean pistols), especially at moving targets at a distance. But if a target is running towards you? It's not as difficult, at least not "farcically difficult". Usually they're running quite directly at you, so all you have to do is basically lower your aim a bit. I've done specific training in exactly this, and it's most certainly doable. Not at 50 meters, obviously, but again, not my point.
Also, I 100% agree that you shoot to kill if that's the only way to save someone, be it yourself or someone else. That's not my point. My point, again, is that not every shot has to be fired with the intention of killing someone, and that some body parts can be considered "less dangerous" to aim for. And that's certainly doable in many different cases. IF you have the choice, and it's a valid choice, between shooting someone in the leg and shooting someone in the torso, and both stop the perpetrator from committing the crime, you should definitely aim for the leg. If that's impossible, and there's immediate risk to yourself or another person, of course, shoot to kill.
My point is, still, that not every shot has to be "shoot to kill". Again, as is proved by the data provided in a previous post, you can shoot someone, stop the crime, and keep the perpetrator alive to face a court of law for whatever punishment is right. It is definitely possible, doable, although more difficult, to aim for a persons legs and stop him from committing whatever crime he was committing.