His intention doesn't matter. His actions, and the previous and ensuing series of events do. He could've gone into the bar to sell Girl Scout cookies and it wouldn't help him.
The law is situational and varies from State to State. In PA, I believe his intentions do in fact matter. Now, going back home to get the gun would probably hurt his case, but if he had the gun on him the whole time in the first place (as many of us would, I carry all the time, even to get the mail), his intentions of talking to the bar owner, who is also his landlord and responsible for the property and lot would count for a great deal.
If he had not approached the drunk (which in this case, he did not), and the drunk came back to him to escalate the situation by threatening and then attempting physical violence, it is very likely this would have been ruled a good shoot.
The law asks that you avoid, and refrain from escalating, it does not say you must hide in your home if you have a handgun. The bar is a public place, not someone's private home. The Shooter would have had very legitimate business being there. His past history of criminal activity would also play into this, as would his observable mental state at the time according to witnesses. Had the shooter had no criminal past, and had his state been observed to be calm and collected, the shooter would likely suffer no felony charges.
Now, being that he left the gun at home, going back to get it and then going to the bar could show him to be looking for trouble. Not enough to convict on alone, but it does create an uphill battle for your attorney.
In your fist-linked thread, this sums it up:
Peterson was the first to display a weapon and this was deemed disproportional force for stopping the henious crime of windshield wiper theft. Because Peterson introduced lethal force into the scenario before there was any justification for it, he was held responsible for escalating it.
He was charged with manslaughter. Had the shooter kept the weapon concealed until after the attacker came at him with a tire iron, I'd bet good shoot any day of the week. He brandished a weapon when his life was not in danger. This has nothing to do with our discussion here. If the OP went outside and said, "move your truck" and waved a gun, then shot the guy a few minutes later, the shooter would be going to jail, same in this case.
In the other scenario, the physical attack and threat had already begun, prior to the shooter getting their firearm. Had he had his gun on him prior to that, despite being threatened by the attacker on more than one occasion and also being assaulted, he has every right to be a patron at that bar as the attacker does and it would have likely been a good shoot. There is no duty to hide. If you can escape, you do. The shooter in this case did escape and came back AFTER the assault had taken place.
In the original post in this thread, NO assault or threat had taken place. A person has no duty to be able to predict the future acts of another person. They also have no duty to avoid a public place due to a wildly possible threat from someone that has shown no aggression towards them. The drunk showed indifference, not aggression. Again, going back to get the gun prior to going into the bar is problematic for a jury, but it does not mean a slam-dunk felony.
Just because you are armed, you have no obligation to avoid places that you may need to use your firearm; otherwise, there would be nearly no scenario that would be a justifiable act of self-defense using a firearm.
If the OP shouldn't have had his gun going into a bar because he had a reasonable fear of physical violence and should have just stayed home, then:
No one could carry a gun into a bad neighborhood at night despite having a perfectly legal and legitimate reason for being there.
No one could carry a gun in the park where mugging and rapes occur; they would have a duty to stay home if armed.
I agree we need to consider the law, but let's not get carried away. The OP should have called the police, however, had he gone into the bar for a perfectly legitimate and legal reason, he only needs to convince a jury he was in reasonable fear of his life over the assault and his intent was not to escalate. Waving a firearm around threatening them is an escalation, shooting someone who is about to attack you with some of their buddies is not.
) so I wouldn't have had some of the options that you did. I'm also not a large enough guy to physically intimidate them just by my presence. I'd have to call the cops or a tow truck in that situation today. 
