Ah, bad drivers and road rage.
When it comes time for the morning commute I put some nice, relaxing music on and pretend I'm about to drive an obstacle course (extra points for stopping someone from cutting me off
). Assuming no one else is going to obey the rules of the road has made my drives much more enjoyable, and safer.
I've had my share of incidents like your son's Marv, and it always pays to ignor them. Unless they follow your son, damage him and/or the car, there's no reason to really do anything. As much as I know we'd all like to knock the guy out, burn his driver's license, and remove their steering wheel, it would just make us sink to their level. Unless there's damage, rise above it.