All in the sake of education. I mean, aside from those beyond help, there are probably quite a few motorists who are simply unaware of the proper way to drive around cyclists. Although, they probably should have failed driver's ed, since I recall my instructor emphasizing the driver's responsibility to be aware of what else is on the road with them and drive accordingly. I think it's called defensive driving. I bet some driver's think this means driving aggressively (hence, the annoying Hooooonk!). Anyway, letting someone know that they were driving in such a way as to put your life in danger is okay. If the message is delivered the right way, maybe the next cyclist they encounter will reap the benefits of your knowledge sharing effort. But, then there are those who will always be a menace to other drivers, pedestrians, cyclists, small animals, inanimate objects, etc.