The shooter should be charged, though I'm not sure whether a jury would find him guilty or not.
Ultimately the question is whether the jury would find it reasonable for him to shoot when he did. Like others have said, the video shows that the shover had taken a few steps back and did not seem to be making a further effort to attack the shooter when he fired. I am of the opinion that drawing the firearm was justified, but by the time the pistol was produced, firing it was not justified. The attacker stepped back and enough time had passed that a reasonable person would not feel their life was imminent danger any longer. Simply put, brandishing the weapon was enough to end the attack and that would be clear to any reasonable person in this situation. Firing was not lawful IMO.
While it's certainly a breach of common civility, criticizing strangers in public is not violence or the threat of violence. Unless Drejka was saying something explicitly threatening to the woman in the car, McGlockton was not legally or morally correct in shoving him. Verbally confronting him would have been acceptable and satisfying to most, while remaining well within the bounds of the law. Call him a tiny-dick busybody and go about your day. Whether a single, forceful shove is enough for someone to reasonably fear for life and limb is something I hope a jury would decide, not the sheriff.
I'd generally categorize the two types of responses from people that carry a concealed weapon. One type realizes that, by virtue of carrying a deadly weapon, any conflict they get into could easily escalate to deadly violence. Knowing such, they act in a way to avoid and deescalate conflicts as much as possible, even in cases where they are legally and morally in the right. Discretion is the better part of valor and all that. I'd like to think I fall into this camp.
Another group sees their hidden weapon as a secret trump card. They act more boldly and feel more inclined to address all the ills of society knowing that, in the likely event of a negative response, they will prevail. These people disgust me, even in cases where they are legally in the right. It's the "I'm not touching you" defense for morally abhorrent behavior. While not written into the law, I find it hard to imagine a jury wouldn't let this kind of poor attitude affect their decision making to some extent in a self-defense case. Most have little pity for those who go out looking for trouble and find it.
I would speculate that had Drejka not been carrying a concealed weapon, he wouldn't have felt so bold in his mission to protect the sanctity of handicap parking.