A final harrowing e-mail on the subject:
About 10 years ago I was driving to work because, although I usually ride my bike to work, my wrist had been fractured when a car had hit me from behind at 40 mph a week earlier. (Luckily, I had my helmet on and although it and my bike were bashed up, I only had the wrist fracture and some deep gravel scratches on my back and shoulder.) I was stopped at a light, one car from the intersection, and a bicyclist ran the light on the cross street, grinning at those of us still stopped at the just-changed light, because he knew that we saw him and would wait.
I rolled down my window to yell at him and instead said, "Shit," out loud because in doing so I saw - in my side mirror - a van coming up from behind me fast in the other, unoccupied lane.
The driver of the van saw only some old fogies still stopped at a light that had changed, and intended to zip right through. The cyclist could not see him and he could not see the cyclist, due to a truck in the left hand turn lane. The cyclist's head was pulped on the asphalt from the impact (both legs broken too) and he convulsed and died about 10 minutes later as I was trying to give him first aid. There were blood and brains oozing out of the back of his head.
If he had not been hit and died, he (a 24-year old Coast Guard Academy graduate, who was a chemical engineering graduate student, a skydiver and a SCUBA diver; I talked with his parents later, who lived several hundred miles away) probably would have told me that it was none of my business whether he ran the light and didn't have a helmet on. However, it was my, as it turned out, and for years I had recurring nightmares about it and was fearful of riding in traffic again.
All right. I give in.