What cyclists should do when drivers yell at them
Joyce Park stashed this in Bicycling
This is funny; however, it's not realistic.
When a driver yells or (hopefully inadvertently) runs a cyclist off a road, they are usually going much too fast for the cyclist to take any kind of action, positive or negative. At the rare chance they care enough to look in the rear view mirror, something innocuous like a hand wave might be perceived as an angry gesture.
The best answer is: do nothing. Cars are a huge danger for cyclists on the road, and in my experience it's best to just keep riding and move on.