I think this has less to do with cycling, and more to do with the mentality of gaining respect for being the guy who shot someone famous. Innit.
Case in point: I went to a Madness concert last night. Now, I am well aware that Madness have their somewhat interesting background in skinhead culture etc. but it somewhat amused me to see people attempting to throw bottles of beer at Suggs and other band members (and, incidentally, other audience members). I say amused, because these bottles of beer were made of very lightweight plastic and were vastly overpriced (like at most festivals/gigs nowadays).
So these fools were spending a half hour or so queuing up to buy over priced beer, and then impotently chucking it in the general direction of the stage. It missed every time. And this was AFTER they had paid the £30+ charge to get in.
That kind of person wants a curious kind of respect..
They would do the same at motor racing if it would have any kind of an impact. They reside on the same step as the sort of weakminded child who throws bricks onto railway lines.