Unfortunately, this goes with the territory.

I use my mirror so as not to be surprised when I get buzzed. I really only get irritated when there are other open lanes right next to the buzzer, yet instead of turning the steering wheel 1/4 of an inch to pass safely they buzz me. That boils my blood. Otherwise I gotta take it in stride or I would be pissed most of the day.

Speaking to the moron will only infuriate you more. You can't cure stupid. Instead of confrontation, I actually use a trick called "thought replacement" (also known as "cognitive-behavioral thought stopping" when I get angered by meat-heads on the road or anywhere. I say a little poem inside my head which (with practice) derails the anger and just melts me right back into the moment. It really works for me anyway. My wife is a therapist. She taught me how to do it. You could probably learn how reading a book and just practicing a bit. There are hundreds of books on this subject - goes well with any stress reduction regimen.

Hang in man. Keep that mirror clean!