Sorry, the guy just fit the stereotype to a T. We were all having a great time on the drive, the driver was pointing out things along the way and talking about the recent history, and then Mr. Know-it-all in the back seat starts whining about how we should take such and such an exit and go down such and such road, and the driver, a nice guy, just kinda clammed up with a really annoyed look, and it got really uncomfortable. Joe Blowhard kept it up until finally I had to say "The driver is a professional, let him do his job!" Turned what had been a fun little adventure kinda sour.

(For what it's worth, the guy with the mouth seemed like he'd probably been one of those kids who got beat up pretty often in high school just because....)