Firstly, I'm sure that there are some sensible cyclists, just as there are plenty of bad car and lorry drivers, but there is a difference: in town if you do something stupid in a car you might hit a pavement or bump another car, but if you do daft things on a bike you will probably get seriously hurt or killed.
Driving through Winchester one dark evening last week I only just spotted a cyclist, dressed all in black, on a racing bike with no rear lights. It was the equivalent of going out on a suicide mission, and when I tooted my horn at him, he gave me the finger. Had I killed him, I have no doubt it would have been seen as my fault.
A geriatric lady riding her bike down Parchment St in Winchester....the wrong way on a one-way street. Try that in a car and you'll be in trouble, but if you're a cyclist...
At the traffic lights on North Walls, indicating that I plan to turn left towards River Park, when a cyclist decides to ignore my signals and come up the inside of me - he only just got away with it - had I hit him I've no doubt he'd have thought it was my fault.
Traffic lights seemingly don't apply to cyclists - watch them and you'll find that most simply ignore them.
Cyclists are, more often than not, total muppets on the road. Fact!