First off, this is an excellent, excellent thread. There are several things that I want to cover, so I'm probably going to get long-winded, which I have a tendany to do, so anyone reading this is now warned!
So...first, dealing with the self-defense aspect of the art...
I think it's all about how you're taught. I think of it like the difference between Miyagi-do and Kobra-Kai. One instructor may teach you to be defensive in your physicallity, and another instructor may teach you to be more aggressive in your physicallity. I also think that it comes down to each of us as individuals as to how we react to a situation.
I, personally, act defensively. I fight defensively. I prefer to try to talk my way out of an escalating incident rather than get it over with. How I react is not wrong for who I am...I'm comfortable with how I handle situations, and I'm very confident that I can handle myself however I need to.
On the other side of the coin, I know of 2 people off the top of my head that act offensively to escalating situations. How they react is not wrong for them...they are confident enough and well-versed enough in their MA's to know how to properly handle a situation using the aggressive approach.
If I were to try to act aggressively, I don't think I would be successful in stopping the situation, and the same goes for the guys who react aggressively naturally...if they try to react defensively, it's probably not going to work for them, either...
What I'm getting at is this:
I'm a big guy. I'm 6'1", around 285 lbs (give or take a few). I'm not in the best shape, but I'm no slouch, either, and I know how to use my weight and size to my advantage in a physical situation. I prefer not to have to use any of my physical skill to get out of an escalating situation. Instead, I prefer to talk my way out of it and walk away...that way, no one gets hurt...
What I tend to look at in situations is this: Exactly why are things fixing to get physical? Is it because I accidentally bumped into this guy in the bar, and his drink spilled? Is it because I feel like this person is coming at me with mallicious intent and I feel my life is in danger?
I like to weigh my options here. If I feel like something's fixing to get ugly because someone's pride (myself or someone else's) was hurt, I'm going to leave it alone and walk away, talking my way out of the situation. If talking and walking away do not work, and the person attacks me anyway, then I'll do what is necessary to make them stop attacking. That doesn't mean I'm going to break the guy's neck Segal-style. If it means that I can move out of the way of the attack and he falls on his face, then that's what I'll do. Nothing more. It's just not necessary...and I can deem what is necessary as I'm a blackbelt...I'll get into that in a moment.
If I feel like something's fixing to get ugly because my life or someone else's life is in imminent danger, then I'll use whatever force I deem necessary to make them stop attacking. In this case, if that means that they won't stop attacking me unless they're dead, then so be it. That would be the last option, after I've exhausted everything else at my disposal.
Now, I mentioned a moment ago that I can deem necessary what force to use. As a blackbelt in TKD, I should be an expert as to judging how much or how little force should be administered to defend an attack properly to render the attacker unable to continue attacking.
I've bolded those words for this reason: If you use force that is beyond what is needed to defend yourself to the point that you are no longer under attack, then you are, yourself, going on the offensive.
Think of it this way: You can view volence levels as you would a scale...with no violence being the neutral point. You have yourself on one side and your attacker on the other. When your attacker begins the attack, the scales are lower on their side, since the scales are weighed down by violence. Your goal should be to even the scales to the point where no violence takes place, and to keep it that way.
Now, it's up to you, as the defender, to decide exactly how much force is going to be necessary to return your scale back to its neutral position...if you have to simply pop the guy in the nose, and he stops, then great...but if you have to subdue your opponent until help arrives to stop the violence, then this should be done with the correct amount of force.
Let's take a look at 2 situations here to demonstrate what I'm talking about. We're going to assume that I'm unarmed, but I don't know if the other person is unarmed or not.
I've just bumped into that guy in the bar and spilled his drink...I've said excuse me, and offered to replace his drink, but he will have none of it. He's dunk, so he's not listening to normal reason. Instead, he contiues to push me physically on the shoulders until my back is against a wall, and I can see him drawing back to puch me.
We'll say that the guy isn't as big as I am for the sake of argument, and that I am 2 inches taller and outweigh him by 50 lbs or so.
As he's drawing back to punch me, I deliver the hardest punch that I can to his nose, shattering it. He flies back into a table and lies still, unconcious. It is later discovered that I have broken his nose beyond the point that it can heal properly, and he will have to have reconstructive surgery done. Not only that, he lost a great deal of blood as he had a lot of alcohol in his system.
That's scenerio 1.
Scenerio 2:
As the guy is drawing back to punch me, I deliver a strong, shoving punch to the guy's solarplexus, knocking the wind out of him. He doubles over, unable to breathe well.
I walk away quickly, not giving the guy enough time to chase after me to continue the fight. I pay my tab and leave the bar.
Now, both of those scenerios have happened before, in real life, but not to me, thankfully. I was present when both happened, and saw what could have and should have happened in both situations.
As far as the legal standpoint goes, I agree that if you're in a physical altercation, you're sunk. Period. Even if you are simply defending yourself. IMO, though, why give the legal system extra ammo to use against you? If you can stop the fight with a small amount of force, then that's what you do. If you know that a small amount of force won't work, then you do what is necessary and worry about the legal consequences later.