Matthew, just a word from someone who used to get very wound up, relishing confrontation in many forms . The adrenaline come-down after any confrontation, whether you win it or not, will eventually make you feel ill.
You are not in a position to educate people by the roadside, and I'm afraid your manner will give some people the excuse they need to confirm their stupidity/aggression/arrogance by arguing back. The guy in the Lotus will never take advice from a young person on a push-bike, so you were only ever going to be wasting your breath.
It can get very frustrating, and on many occasions downright frightening when drivers make stupid and dangerous manoeuvres, but you have got to just let them go. Post them on Youtube and tut at them if you want to , but you will very, very rarely feel better after confronting anybody.
You also need to bear in mind that this sort of behaviour is nothing personal. Try to think that they would have drive like that no matter who or what was there, and realise that you are not a deliberate target of malicious behaviour, but simply a coincidental subject of stupidity. This helps to reassure you that he wasn't doing it to hurt you or frighten you (no matter what the outcome) it's just that he's utterly selfish and stupid. Use this thought to add a feeling that you are far better than he is, and you already have the upper hand. He doesn't need to know how stupid he's been. It wouldn't make any difference, and deep down I expect he already knows it.