here is what i was taught back in the police academy back 10+ yrs ago. i think it basically holds the same nowadays. the issue here is not necessarily winning the fight but winning the ensuing court battle.
if it was pure survival in a lawless world then 100% of the time go to firearm and engage BG since it is going to be the most effective and efficient way to put a BG down with no risk of getting into any sort of legal trouble.
now having said that, i think the issues are:
1. being reasonable in the eyes of the law, and
2. simple but effective ways to ensure your safety without always relying on a firearm.
Given that premise, I hope I can give some input.
Police officers are given a "force continuum," or a type of ladder for escalation and de-escalation of force. from bottom to top they generally are:
command presence
voice commands
hands-on (come alongs, low profile wrist lock)
physical force (punches, elbows, kicks, etc)*
canine*
OC (pepper) spray or chemical agent*
taser gun*
flashlight/baton/other impact weapon*
less lethal weapon (pepperball/beanbag projectile)*
deadly force (firearm/vehicle)
everything with a * above denotes "intermediate" force, all of which are on the same level (i.e. canine is not below O.C. spray, they are the same level) so when you get to intermediate force, you can use any of these so long as you can articulate why you chose one over the other, i.e. "i chose the flashlight because it was already in my hand and because utilizing O.C. spray inside a crowded bar would have caused a panic and possible stampede, jeopardizing public safety. a canine, taser gun, etc was not available inside the bar."
however, the standard is not the same for police as it is for civilians, especially CCW'd civilians. a police officer is not expected to walk away from confrontation, instead, is expected to attempt to diffuse the situation and then take someone into custody if need be using whatever force is deemed necessary to effect the arrest.
a citizen usually will be asked why he/she did not leave the scene in order to diffuse the situation. a CCW'd citizen, carrying a firearm, will be expected to leave the scene. if he/she stands his/her ground and ends up using deadly force, the issue will always be "had he/she left would this have become a deadly force situation?"
the flipside of that is if you cannot reasonably leave, i.e. the BG is blocking the only visible exit, then legally you should be covered "i couldn't leave the scene because the aggressor was preventing me from leaving" [i.e. false imprisonment].
simple assault in and of itself is not a valid reason to use deadly force. if it was the cops could shoot everyone that pushes them or otherwise assaults them. so if someone pushes you or otherwise commits a simple assault I think if you pulled out a gun and shot them you would probably be charged with a felony.
you could, however, defend yourself from attack by countering his assault with pepper spray or a fist. you could very easily defend yourself from prosecution when using pepper spray if the person made an aggressive advance towards you, since OC supposedly does not leave permanent damage. nowhere in the law does it state you must be struck first before you can defend yourself. an assault is defined as "an attempt coupled with present ability." so if someone cocks their fist back he has committed an assault. similarly if someone points a gun at you he has committed aggravated assault, regardless if he's fired a shot at you.
in the pizza parlor incident, i don't think this guy was expecting this big behemoth to come in and punch him silly. i think after the first 2 or 3 hits, if the guy was CCW'd he probably could shoot him and get away with it legally. a person that large, when seen by a jury, will most likely take the position of the victim. the large BM assaulted the WM for no reason and was over twice the size of him. nobody came to the WM's aid as well. he could have easily argued as a CCW holder that he felt in fear for his life because of the relentless assault and that he was about to go unconscious, at which time the bad guy may find his weapon and kill him with it. i think after seeing that video, not too many D.A.'s would try to hang that guy for a homicide charge. you could have run all the way up the force continuum with an impact weapon and you probably wouldn't have incapacitated him unless you started breaking bones.
i have started advocating carrying an intermediate force weapon in addition to a weapon if you are CCW'd. it gives you another force option between hands and gun. i recommend O.C., but a mini maglite or SureFire light would also serve as an impact weapon as well.
it looks better to a jury as well if you tried O.C. or another less lethal force first but failed.
keeping that in mind, do not ever think you are compelled to attempt nonlethal force first before going to deadly force. if the BG pulls a knife or a gun or tries to run you over or whatever, bypass the intermediate force and meet deadly force with deadly force.
having said all this....im not a lawyer or an expert witness!