you are clutching at straws hugely. The crux of this argument is this : some people wear headphones when out walking, others don't. Some people get hit by cars when out walking, some of these people (a very, very small known proportion) are wearing headphones. Is there enough evidence to suggest that those getting hit by cars happen as a direct result of their headphones? If there is, you certainly haven't provided it despite your claims. Your 2 much vaunted studies concluded firstly that there 'may' be a risk posed but further research is required to prove if so, and the second grouped headphone use in the same category as things like talking to friends and eating or drinking. Hardly abhorrent behaviour. And even then, there was only a weak correlation.
If you went outside now and did a head count of all people you saw wearing headphones, I'd wager you'd see AT LEAST 1 in every 50, most likely more. Now that's conjecture, but I'd be very surprised if it wasn't right. If that is the case, in fact if it's even only 1 in 200 (highly unlikely) that still suggests there's no extra danger in wearing headphones for a pedestrian based on the figures we know.
The car example is perfectly valid - you have absolutely no proof whatsoever that any given journey is a 'benefit to society', what nonsense. In fact, I'd bet a large number of car journeys in an urban environment would fall under the category of an 'unnecessary luxury'. And where did I mention banning cars? I just asked if you perceived other drivers to be ignorant and stupid, on the sole basis that they're driving? Statistically there's far more chance they'll endanger you than any runner by the side of the road with headphones on.
If someone is wearing headphones and doesn't check for traffic when crossing a road then that is negligence on their part, absolutely nothing to do with the music. If they're hit by a car whilst on the pavement then that's not their fault and they almost certainly would've been hit if they hadn't been wearing headphones. The sole example you gave early in this thread of how he was supposedly 'endangering' people was everything to do with negligence on the part of the runner and nothing to do with whether or not they were listening to music.