"The question is, accepting that cyclists are an even cross-section of society and beyond control.....what should be done?"
That is just it: we, as cyclists, aren't an even cross section of society. If we were, there wouldn't be a problem.
I think actually that cyclists are a pretty even cross-section. To be clear, I don't mean that many people cycle, I mean that if you look at people who do cycle they are all kinds of people.
When I think about rides I've been on, I've ridden with guys who worked in the shipyards or as brick layers, one who works shifts fixing streetlights on motorways (!), electricians, engineers, doctors, students, vets, "vanilla" mothers, people who are on long term dole and people who earn serious money, you name it.
That's what I mean about collective responsibility. It's just daft that people will drive aggressively at a big-money financial director because a homeless guy on a stolen bike was riding on the pavement the other night, what connection do they think there is? It's like picking people out because they have moustaches.