Okay, now I have spoken to the District Attorney about the case, and about how the general principles of self defense apply to dogs that are attacking (or appear to be attacking) people.
The D.A. recognizes the right of citizens to have guns, and carry them with a GFL / GWL.
She understands that dogs sometimes attack and bite people, unprovoked, and under some circumstances you can use a gun if you reasonably believe the dog is serious about biting you (like a few dogs are) and not just barking at you as a stranger for walking / cycling / jogging past the dog's home (which many dogs do, even "friendly" ones).
This case had yet another fact very much against the defendant's self-defense claim: The dog had been following the man for some time, barking at him (and maybe snarling, showing teeth, etc.), but never attacking.
The dog kept his distance from the man and just basically harassed him, and the man and the dog walked up the street for a pretty good distance before they both arrived at the home of the dog's owner.
THEN the dog's owner came out to get her dog back.
THEN the guy was screaming, swearing, and raising a big stink about how he "could have" or "should have" shot the dog dead.
THEN he pulled out the gun, which he had with him all along (he had a GFL), as if to emphasize to the woman that he had the means to kill that dog. The woman thought he was going to shoot the dog right there at her feet, even while she had him back on the leash.
So she let go of the dog and backed off, and the guy was once again facing a barking, yapping, excited dog (just like he had been as he walked up the road with the dog just a minute or two before).
THEN he shot the dog. 3 times. Once or twice AFTER it was down, bleeding, not moving.
It sounds to me that the dude made up his mind to shoot the dog, as he considered it a nuisance animal.
OTHER THINGS TO KEEP IN MIND:
1-- If you as a defendant choose to exercise your right to remain silent and not incriminate yourself, you don't have to testify in your own case, but then the jury only hears ONE side of the case (unless the defense attorney gets really lucky and a State witness says something pro-defense on cross-exam, which is very rare).
2-- If neither you nor any of your close friends or family members testify that it's your routine and habit to normally carry a gun everywhere, you might face the possibilty that jurors will suspect that you took your gun with you on this one particular date and time because you expected trouble, and were looking for trouble.
3-- People who go looking for trouble will have a hard time invoking a self-defense claim, especially when they brandish a gun during a verbal argument with somebody else. Although Georgia doesn't have law against "brandishing" that uses that exact word, it's not a smart thing to do. It doesn't make you look like a reasonable law-abiding citizen to prosecutors, witnesses, or jurors.
4-- In this case the guy MIGHT (I say "might") have been legally in the right to shoot the dog IF he had drawn and fired when it first came after him. But by waiting and observing that the dog was NOT pressing the attack, and merely barking his fool head off from a few feet away, never coming closer, the "green light" to shoot turned red.
The passage of time changed the circumstances so that it was no longer reasonble for this guy to be in fear, and the jury didn't believe he was in fear. They thought he shot the dog out of anger, not fear.
5- It would help you in a self-defense-against-dog case IF you tried to use some other means to stop the attack. Going straight to the gun and shooting to kill (shooting center of mass) can be too much. It might benefit you to escalate the force. Start with shouting, kicking or hitting the animal, using pepper spray, etc. before bringing out the deadly weapon.
Obviously sometimes you won't have time to do all of that. But if you did have the time and only shot the dog after trying some other alternative that didn't work, THEN it would be unlikely you'd face any charges, and your defense would be much stronger if you ended up in court later.
That's what I learned today. So between talking with the defense attorney yesterday and the prosecutor today, I'd say I learned a lot.