Originally posted by Juha
When this sort of thing happens to me, I want them to know it was a close call, and a slap on their car gets their attention better than anything. I do that regardless of age or gender. Quite often that is all that is needed, but I have gotten into a couple of (peaceful) conversations, where I have explained my position and sometimes my legal rights as well.
Knowing is one thing, caring is another entirely. If someone cuts you off, it's possible that it may be because they don't believe bikes have any legal rights to be on the road. Hitting their car is not going to make them aware of that (or change their views). Exactly how much damage do you think was done to the car? A lot less than if they'd decided to let the car roll over you.
If you're really worried about the way someone drives, take down their number and call the cops. Phone calls from the police tend to be just a
little more persuasive than harmless smacks on the frame of a car.