I don't cycle as much as I once did - work demands, etc. have curtailed the time I have to spend on the bike. I never commuted, but used to ride a good 3-4k miles per year. I feel it a bit presumptuous to conclude that riding, when in lieu of driving, has any appreciable effect on the cost of gasoline. It makes sense to conclude that there is an impact on the use/non-use of fuel, but the cost of that fuel does not bear a direct correlation to the use of or demand for same.
I remember periods in my community where there were public drives to reduce the use of electrical power. Surprisingly, the cost of power rose in response to our successful efforts to reduce consumption - the reason? The reduced usage, according to the local utilities, dimished their economy of scale, thus forcing them to charge more to supply less electricity.
To this day, I am not certain I buy the explanation, but, whatever the reason, power costs per unit of power increased, and that increase remains in effect today.
Anyone who consumes fuel to power a vehicle is aware that any natural or political event perceived to threaten supply will result in almost instantaneous rise in the cost of supplying fuel. Relaxation of those increases, if they occur at all, generally come at a much slower pace, and, generally, do not match the level of original increase.
I sadly conclude that, if cycling resulted in x% decrease in the use of fuel, the cost per unit of fuel would raise by at least an amount sufficient to offset the revenue lost to the suppliers of that fuel as a result of the decreased demand, said conclusion based upon my lifelong observation of this issue.
If you are inspired to ride more due to an opposing opinion, then that is a win for you, no real loss to society. Keep on keeping on, but, in terms of having an impact on the never ending battle to reduce the use of fossil fuel, you are jousting at windmills.
Just sayin', and I regret that I don't ride as much as I used to ride.
As for the parking issue, my encounters while riding (and parking) have more often involved some "motorized" person claiming that I should not share his/her space or take my own, owing to the fact that he/she pays road and fuel taxes, and I don't. Most of those situations have been diffused by my display of my drivers license and explaining that, as the owner of a car, I, too, pay the same taxes. This may or may not be true for those of you for whom cycling is your main mode of transportation. Of course, if you never make use of a motor vehicle, you might naturally counter that your use has little, if any, negative impact upon those roadways of which you make use. The motorist will not likely buy that argument, but it is true.
This was an interesting thread that I enjoyed reading. I apologize for the long post. Happy cycling, all.