It really depends on the situation. I did recently confront someone and when I posted the story on here, I got sort of slammed by a few others on here (even though the worst I did was call the lady a moron because she was looking down in her wallet instead of straight ahead). I think you have to take each situation for what it is. I had a "confrontation" with a woman about year ago. It was completely civil and I was incredibly polite, but serious in conveying that her actions could have just killed me. She had two young kids in the car with her and had almost run me off the road while turning into the grocery store because she was playing with her cell phone (I was riding legally in a bike lane). When I confronted her, I asked her if the two kids in her car were hers. She confirmed that they were. I said something like, "Well, just like I'm sure you like people to watch out for your kids, my mom, who lives just up the road, likes it when people watch out for me. I certainly hope you'll be more careful in the future." I could tell by the look in her face that this REALLY registered. Who knows, it was maybe one of those events that stuck with her and saved someones life down the road.

I do think cyclists have a responsibility to educate non-cyclists, but I agree that it has to be done within reason. I don't condone the destruction of property, but I do condone civil confrontations that hopefully teach a lesson.