I think the ones that don't use their common sense are drivers.
Recently I was out on my bike with my son on his bike and we had to go 0.2 miles along the main road (30mph limit), then turn right.
The driver behind did not overtake, which is in accordance with Highway Code advice generally (don't overtake near junctions, etc.), but the one behind that started beeping his horn repeatedly at him. This was rather off-putting to us and we ended up turning when it wasn't entirely safe to do so.
Was there a queue behind us? Yes there was, five or six cars. Was anybody actually delayed, no they weren't.
I've been beeped for not overtaking a cyclist before too, in my car; given that the cyclist in question had just past me in the queue and there was traffic all the way ahead, there wasn't much point in rushing past.
While the situation might be different in other parts of the country, I have never witnessed a sitatuion where a cyclist has genuinely caused a delay - a short queue sometimes, yes, but are those behind actually getting to their destination any slower? No they are not, when they pass the cyclist they just accelerate to the next red traffic light. It's a nonsense.
I've spent four hours on the M25 before (in my car), due to congestion caused by motor vehicles. The idea that cyclists cause congestion is utter nonsense. Take for example school run time, you get big congestion through the town here, purely caused by parents picking up kids from school. It's got nothing to do with bicycles, because there are so few of them on the roads, and if parents switched to bicycles the reality is the congestion would go.
Personally speaking if I'm in an urban scenario (traffic lights, queues), I will always ride in the middle of the lane, to discourage the idiots who think that it's a good idea to try and squeeze past me to get to the next red light quicker (where of course I can filter to the front of the queue).
It's pretty breathtaking, given the numbers of cars on the road relative to the number of bicycles, and given the amount of congestion in places where there are no bicycles at all, that motorists blame congestion on cyclists.
You are not stuck in traffic, you ARE traffic. Not someone else, not bicycles, YOU are the problem, you are using a scarce resource (road space) at a time of peak demand (school run), blocking the entire lane, then presumably obstructing the road (all cars parked on the road obstruct it) when you park at school, getting in the way of cyclists trying to go about their business (which is at least as important as yours) and generally being anti-social.
www.flickr.com/photos/carltonreid/5260106747/
Sorry to be blunt, but school running is highly anti-social. Bikes getting in the way of the parade of SUVs are neither the problem, nor the hazard!!!