Ash, I sympathize with your point. But this is one circumstance where disdain for the group is well-earned by far too many of its participants.
I'm in Portland, and daily come into contact (all too often, almost in the literal sense) with urban bicyclists. There are those who are courteous and respect the rules of the road, but there is also a significant minority who simply don't care. They claim the rights of motor vehicles, but obey the laws only when it's convenient, and heaven help anything or anyone (e.g. pedestrians) who get in their way. Stop signs? Ha! These guys reinforce the public image of Lance Armstrong-style arrogance on two wheels.
There's a lot of truth in that Portlandia clip I posted above.
Anti-aviation sentiment is based primarily on fear and ignorance. But almost everybody at one time or another has ridden bicycles, and has probably enjoyed the experience of doing so. So public disdain for hard-core, aggressive bicyclists results from experience.
Bicyclists could clean up their act and improve their own image. But given human nature in an inherently unregulated activity, don't hold your breath.
There are no shortage of idiots out there. Some people, for example, think it's funny to make death threats against bicyclists! And some idiots ride bicycles, it's true.
I ride a bicycle, and a motorcycle, and I drive a car and fly airplanes. I try to do all of those things responsibly.
When I've ridden my bicycle, I've had cars pull in front of me and rapidly stop, been squeezed into a sewage gutter by an SUV, had cars blow through red lights and almost into me, and had busy suburban mommies throw open parked car doors just as I was coming past. Lots of idiots in cars.
On a motorcycle, I've had all the same things happen. Some people are more aggressive towards motorcyclists than towards cars. I've noticed that none of these "heroes" gets out of their car to talk to me face-to-face. They like to stay in their safe steel cages.
When I've driven in a car, I've also had all the same things happen. Idiots driving right up on my tail instead of passing on the highway, idiots stopping suddenly in fast traffic, swerving across multiple lanes of traffic, applying makeup or texting while driving.
All I'm saying is that there are no shortage of selfish idiots out there. Some of them ride bikes and motorcycles, but in terms of sheer numbers, most of them are in cars.