I'd like to propose a theory to explain what Expatriate refers to as contempt for the automobile and hence those who drive them. I would first conjecture that there is a wider range of response to the automobiles (and their drivers) on the part of most cyclists who live, or try to live, as car-free as possible. That range runs from respect, empathy, sympathy, pity, through shallow disinterest to outright hatred. And for those of us who have lost friends in collisions when the damned things are driven by drunks or other mentally compromised individuals these feelings can be deep seated to say the least.
My theory is drawn primarily from observations made by
Marshall Mcluhan, a social visionary and popular culture theorist known for his work in the 1960's and 70's. He made this observation about the automobile:
He observed that our technology had become extensions of the human self. Just as we are collectively interacting right now on the internet we collectively interact with all technology. Thus a common experience of many bike riders is the feeling of becoming "one with the machine". The bicycle is then an extension of the physical self. The cranks an extension of the legs, pounding in a rhythm with the heart and the lungs, the wheels as a further extension of the legs and the feet. Anyone who has experienced this, whether on a rapid mountain descent or flying through traffic on 6th Avenue, knows viscerally what I am talking about.
The automobile is likewise an extension of the physical self but in a vastly different way. The panoramic visual landscape is compromised. The windows function to deflect air, the roof shields out light, precipitation, the body of the car filters the vast percentage of sounds and smells. The automobile is thus, as Mcluhan so eloquently describes, "an aggressive shell". The experience of driving the automobile (the extended self) tends to be one of distancing the driver (the inner self) from one's environment. The technology not only is a highly effective protective barrier it is also extraordinarily more powerful than the human being without it- hence, it's threatening or at least imposing presence as contrasted with a bicycle.
Since both the bicycle and the automobile are extensions of primarily the human being's locomotor system they both impact what is referred to in biology as "the degree of cephalization"- basically brain size in relationship to body mass. The impact of the bicycle is far more manageable because it's power is relative to the strength of the rider and it's weight and mass is offset by the increase in the human's energy efficiency- so it has little overall change in degree of cephalization. The automobile, however, has proportionately higher mass than the human being thus vastly reducing the degree of cephalization. This is why a child, with a not fully formed brain function and still developing motor skills, can ride a bicycle but would be lethal behind the wheel of a car.
So, basically, no matter how smart we are, or how smart we think we are, we are all "stupider" behind the wheel of a car. We are also, due to it's design, size, mass and power inherently more aggressive and dangerous to those around us. We have more akin to a rhinocerous than a human as soon as we step into a car and shut the door.
What you're sensing as contempt is legitimate fear accompanied by mock displays (pounding on car hoods, kicking doors, flipping the bird etc,) of aggression on the part of cyclists. These displays are necessary to keep these very dangerous beasts away.