Take My Grandpa's License Away!

I just picked up my contacts from the eye doctor and decided to take a spin through Starbucks' drive-thru before hitting the highway back home. I made it safely through the round-a-bout onto a four lane semi-busy road. I'm driving along and coming up to an intersecting street. All of a sudden a silver Ford Focus tries to make a left turn in front of me from the crossing street. I do not have a traffic light or stop sign, mind you. They, however, do! I had to swerve, honk my horn and yell "WHAT THE FUCK?" (pardon my French).

Then I realized it was my grandfather. I swore at my grandfather. My heart was racing, and I'm not quite sure if the surprised look on his face was that of recognition, or fear of being hit. If I see him on Christmas, am I supposed to bring this up? What is proper protocol for handling this situation? I should check out the Hallmark aisle at the store to see if there are any cards for the occasion.