A lot more useful to focus on Prevention rather than on Vigilantism. The first is more likely to save death and injury. The latter may well get you in more trouble than you can handle.

Fact is society world wide is less courteous and seems to be more absorbed in the toys inside their vehicle or plugged into their ears. Yesterday, while driving, another vehicle ran a Stop sign barely missing me in my vehicle then ran a second Stop sign when entering a main highway. Didn't look around either time. Cyclists are no better or worse, just a different vehicle.

So, make yourself as visible as possible, motor or pedal power, keep your head out and operate as defensively as possible.