I hope you vitriolically react with "you're a f@#$^!n dick, man" or some other kind of pressure to get him to get the message: "endangering others is bad and you're losing respect/status by doing so."

My truck driver friends improved fairly quickly after I sat shotgun a couple times

What a weird reaction. How could you correct something like that? Better parenting?

I'm thinking of flashing my high beams whenever I pass drivers with lights too bright. Maybe they're just not aware. I flash my highs at drivers with their headlights off at night because it's dangerous. No reason to not do the same when it's dangerous on the other end of the spectrum.