The proper thing to do here is ride up next to the driver's window and when he rolls it down tell him
"Comcast hates puppies; I ride a bike to save money on my commuting cost to pay my Time Warner bill which saves me enough money to buy puppy food. You almost killed me with your failsauce driving, therefore you would have stopped me from getting puppy food - consequently your company hates puppies."
Not sure if he'd get the joke.
You could also just do the more traditional
"Hey *******, was your nom nom more important than not killing someone in the company vehicle? What's your name dickface so I can call in your perfect driving, oh, and say hi to Marj at unemployment for me, and let her know the anger management class worked well - you're ass is still alive and ready to order."