Point taken, NavyLCDR. BTW, I was a NavyLT aviator back in the day. Yes, I would have the same concern with a vehicle for the very reasons you mention. So I would not do a private sale of a car to anyone I did not know well. With one exception, all the cars I have sold have either been to family members, or dealers. The one exception was that I sold an old Mercedes 190D to a fellow Navy officer I did not know well when I left Pensacola. I thought Nav-to-Nav was acceptable.
But even if I did do an open private sale, I see a difference. If I sell a car, it's pretty clear what I'm responsible to do by law. If the buyer misrepresents himself, the law will be after him for fraud. If he misuses the car, I would feel bad, but I would not be legally liable. With a gun, I think "the bar is raised." If someone buys a gun from me using a false ID and then goes and shoots up a mall, I would feel devastated and I would expect both the law and the media to be all over me.