The thing is how high should the standard be to claim self defense. Can you initiate a confrontation, escalate it and still claim self defense or should you have a legal obligation to avoid violence? These laws get rid of that and so if the dead guy had a walking stick he would probably get away with it.
And that's where investigating things, and taking them to court when they're not cut and dried, comes into it.
There are some things that are clearly self-defense. If the cops find two known car jackers lying dead next to your car, at an intersection they've been known to jack cars, and they both have weapons lying close to hand, it's incredibly unlikely that you set them up in some deranged vigilante plot.
But there's a whole spectrum of possibilities that start there, and range down to things so ridiculous that even these laws couldn't get you off. At least, I hope everyone will agree that "He was looking at me funny so I shot him!" isn't an acceptable defense.
What's reasonable will depend on the entire context of the altercation. You mention "if the dead guy had a walking stick he would probably get away with it", but as I said before, even that isn't reasonable. A guy with a walking stick who is in front of your SUV isn't a threat, at least not to anything more than your paint job. If he moves around to the side of the SUV? That's starting to become a threat, as now he could in theory be close enough to smash a window and brain someone in the vehicle. If he really starts smashing at the window, that's pretty clearly a threat, but it might not be a "deadly threat", as car windows are actually harder to smash than most people think. See, it's these kinds of things that need to be sorted out. A blanket "I felt threatened!" Get Out of Jail Free card is ridiculous.
What we need to accept is that "Self defense" is a
defense against the accusation of the crime of murder. What's not disputed is that one guy is dead, and the other killed him. If that were the only question at law to be decided, the guy would be guilty and in jail in no time. The real question to be decided is, was the shooter justified in shooting under those conditions?
What level of "threat" we decide to agree is reasonable to justify the shooting can be discussed. And it's possible to have a standard that is too ridiculously
high as well as too ridiculously
low. Compare some of the cases in the UK, where people have been charged with murder or attempted murder when dealing with actual criminals who were actually engaging in crime at the time, with a case like this. I suggest that these are the two ridiculous extremes, and that we need to avoid both of them.