I think the OP does bring in some good points though. If you do carry a weapon, you should be held to a higher standard. You have the ability to end someone's life right then and there. Even if they are wrong, you're taking a life, and without a doubt it's going to hold a huge place in your mind killing someone regardless of how justified you are.
When people start fights at the bar, unless you're directly involved, GTFO. If a fight breaks out and someone bumps into you, you have a choice to get out of the way and let the idiots fight, or you can jump in there being macho and pull out your gun and escalate the fight. Sorry, but if it were me, I'd get out of there. The point is why fight unless you have to?
I'm not saying you need to retreat to the closet of your house when someone breaks in, but I think if you can make a REASONABLE attempt to diffuse the situation or GTFO, do it. It's just like the boating analogy of CLite. Even take driving for example. When someone runs a red, you make an effort to dodge that car if its about to hit you. You obviously could just take the hit and then sue the fuck out of the guy because he's wrong. But in many accidents it's never ruled 0% your fault. It's like 70/30 or 80/20 or 60/40, 50/50, etc.
Anyway, I do think that before you pull your gun in self defense that you should be certain that you are in grave danger, but at the same time I don't mean that you should let the perp stab you before you decide to pull your gun. There's logical limits. When fights break out, if you escalate with your weapon, chances are someone's going to get hurt, especially if the other side doesn't back down. Thus, before you pull your weapon, you should probably make sure that its the only way out of the situation (obviously without putting yourself at severe risk).