I hear of these situations rather frequently. I am often amazed at how our anger at being cut off, drives us to these decisions. Consider that from the moment you reach out and damage the vehicle, 2 things are now true: 1- you are responsible for a crime (property damage), and 2- you may just have ignited the fuse of someone who will immediately turn to road rage, and run your arse over. Is "lane position" and being in the "right" that damn important? Why not simply roll off the throttle, let the dope take the space, then pass him at an opportune moment and be on your way. Shake it off, shrug your shoulders, and forget about it. It WILL KEEP HANPPENING. It's part of driving and riding these days.
Without question if a biker damaged my car for such a silly reason, I'd introduce him to my shoe laces. After I found him in the ditch from trying to evade me.
If the horn doesn't work, try the damn brakes.