I'd agree wholeheartedly with the complexity of trying to change attitudes, an observation I've made previously is that the only person whose attitudes you can change is your own. I'm always interested to see how much my behaviour affects others; for example, I've often felt that by stopping at red lights others stop (especially those you have seen RLJ-ing previously) and I know that by taking a good line around cyclists when I'm driving, those behind copy me (as opposed to the people in front, if you get my drift).
But saying "I can see no reason why more training would make adult cyclists behave any better than car drivers" misses the point. Car drivers are MOSTLY not that bad, and they are certainly not different animals to cyclists. I would say greater than 90% of car drivers in the UK obey traffic signs and lights. The greatest issues of dangerous lawbreaking in my view are mobile phone usage and casual speeding, I doubt that the attitude change needed to alter that is likely to happen soon. If and hopefully when it does it is likely to be as a result of greater numbers getting on bikes and seeing those activities from a different perspective.
But back to the original point. Yes, I do think that it would be good if cyclists in general came up at least to the low standards set by drivers. There is a utopian day when actually it won't matter if you do, say, turn left on a red light but until then I assert my right to be a vehicle on the road with the same rights and obligations as cars. Painting all drivers as badly behaved, murderous and unthinking is part of the problem.