Some issues with this story:
- How is it that he heard two guys talking quietly in his front yard, but didn't here the rollover? And, according to the way you tell the story, they didn't say anything, just point to the yard. Seems to me there's either something he's not telling in the story, or he doesn't have a clue how to tell drunk and stupid from hostile and cagey.
- Seems to me the Constitution gives everyone the RIGHT to own a gun; it doesn't say everyone HAS to own a gun. As Fuzzybunny said, If Bill doesn't want one, that's cool, as long as he doesn't decide that no one else should have them either. Gunowners forcing people uncomfortable with guns to have them is just as bad as antis forcing us to give them up.
- Bill had a "significant emotional event." You may be able to show him the logic of the situation (he properly read the situation, held fire, etc), but he's wrapped up in the horror of the event and what he might have done. People sometimes lock onto what COULD have happened instead of what DID. Instead of learning that it's important to be REALLY, REALLY, REALLY sure of what your doing, he learned a different lesson--that the presence of a firearm sometimes escalates things when not required. A valid lesson, but he drew the conclusion that the way to solve the problem is no guns, instead of training and clear thought processes. Because it's an emotional, not a rational, response, I doubt you will be able to change his mind.