I cycle more than I drive, and regrettably, ride. I have seen plenty of idiots driving fast cars and riding motorbikes inappropriately. I have commented to individuals when I've caught up to them in traffic, and I have been threatened with a lump hammer which one arsehole pulled from his door pocket. I have also been told to get a bike license by a bloke who accused me of cutting him off by moving out to the middle of the road, when I saw the car driver, illegally parked, facing into the oncoming traffic and indicating to pull back to the correct side of the road for him. He presented the greater danger to me, and the blind bend just after the parked car. The motorbike was quite highly revved on it's approach, and I had seen him coming on an earlier check, but he gained on me rather fast, on a 30mph road. When I caught the motorbike at the next junction, as I was about to comment that I'd most likely gained my license more recently than he had, he shot off from the cycle box, turning left without indicating, cutting me off.
It is easier, and clearly safer, to voice an opinion over an internet forum. Speed has a place and a risk attached to it, I understand that, but cycles are not expected to be traveling at high speeds, and motor vehicle drivers have a hard enough time seeing the ones at 10mph. I have a gap in my memory which starts with leaving home in the morning, and then waking up in hospital in the afternoon. My tourer was never the same after that having been cartwheeled. Not one person saw how I crashed on an otherwise very busy road. At least on a motorbike, I would've had a bit more protection.
I have driven fast, a loaned G27 at a charity track day, and my own G20 roadster and with my landrover. I have also all but written off the landy, on a snowy snake pass, all of it with youthful ignorance. These days, there's just too many cameras and average speed traps to make it not worth the risk.