Digressing slightly, when I was doing my GCSEs I studied the play Professional Foul (by Tom Stoppard). It's set at a philosophy conference, and one of the quotes has stuck in my mind: "There is a sense of right and wrong which precedes utterance." The philosopher gives the example of a small child who instinctively cries out "That's not fair!" In the case of drivers, they probably feel that it's unfair for cyclists to get all the same benefits without paying the costs. That's understandable, and I don't want to squelch anyone's sense of natural justice, but in this case I think that it's based on misconceptions.
There's no legal obligation for cyclists to insure their bikes. By contrast:
You have to have motor insurance before you can drive on public roads.
Third party insurance is the legal minimum. This means you’re covered if you have an accident causing damage or injury to any other person, vehicle, animal or property. It doesn’t cover any other costs like repair to your own vehicle.
(Source: Vehicle insurance - GOV.UK)
Insuring a bike against theft is a separate topic, which I may come back to in another post; if I don't insure my bike, and someone steals it, I'm the only person who's out of pocket. For now, I'll just focus on third party insurance.
I'm a member of the CTC: I pay £41/year for adult membership, which includes £10 million of third party insurance. Similarly, members of the London Cycling Campaign get £5 million of third party insurance, and it costs £34/year to join.
So, right away that means that anyone who says "You don't have insurance" to me is wrong; there are plenty of other cyclists who also have insurance. It would be better to ask, and then complain if the cyclist says no. Also, bear in mind that the insurance company will only get a portion of the membership fee, which makes this very cheap compared to insuring a motor vehicle. I assume that the insurance company have done a risk assessment to justify it, so they're not expecting to pay out very much money from these policies. In other words, they think that cyclists are less likely to cause the same amount of damage as car drivers. Looking at the physics of it, momentum = mass x velocity. The bigger you are, and the faster you go, the harder you hit. Cars are bigger and faster than bicycles, so they have the capacity to do a lot more damage.
Still, if the law changed to make cycle insurance compulsory, I'd have no objection to that. It wouldn't make any difference to me personally, and I don't think that the extra cost would force any cyclists off the road.
First things first: "road tax" is a misnomer. People use that phrase to refer to the tax disc on the windscreen, but it's technically called Vehicle Excise Duty (VED). This is based on engine size (for older vehicles) or on fuel type and CO2 emissions (for newer vehicles). Since bicycles don't have engines, don't use fuel, and don't produce emissions, there's no duty to pay (except for trade licences). The AA use the term car tax: that's better, because it doesn't imply that this is a toll to use the roads. However, this duty also applies to other motor vehicles (e.g. motorcycles and vans), while it doesn't apply to all cars (e.g. electric cars are free).
The other issue is that this money doesn't specifically go to pay for roads, i.e. it's not "ring fenced". The old road fund used to work that way, but Winston Churchill abolished it in 1937. Instead, all the tax goes into one big pot: that's VED, VAT, income tax, etc. (Council tax is separate, because it's local rather than national.) A certain proportion of this money is then spent on roadworks. I don't know what the proportion is, but that's not relevant here. Whether it's 1%, 10%, or whatever, if you pay more tax overall then you'll also pay more money towards the roads. So, either nobody pays road tax or everyone does, but cyclists aren't getting special treatment.
Suppose that a particular driver pays £135/year on VED. If you're in the 20% tax bracket, that corresponds to earning an extra £675/year. If you're in the 40% tax bracket, it's equivalent to £338/year. So, a cyclist who earns an extra £1000/year compared to that driver will be paying more tax overall, and therefore paying more money towards the roads. Does that mean that the driver should get out of the cyclist's way? Then again, this ignores VAT, and drivers will pay extra tax on fuel. So, if you have two cars at a crossroads, should the drivers compare mileage to see who's more entitled to come out first?
Personally, I pay more tax now (as a cyclist) than I did just after I finished my undergrad degree (when I bought a car). At the same time, I'm sure there are drivers who pay more tax than me. However, the whole point of the British tax system is that you don't get special treatment just for paying extra. For instance, if I go to hospital then they'll triage me based on my illness, not my wallet.
I don't think there would be any point in forcing cyclists to get tax discs, since these would all be zero-rated: it would cost money to print and issue these (and enforce non-compliance) with no benefit in return.
Edit: Tax discs are being abolished; they won't be issued after 01-Oct-2014.
That said, I do think it's a bit unfair for drivers to pay tax on vehicles that are sitting idle. Since the VED is now based on emissions, I'd prefer to eliminate it altogether and replace it with a higher tax on fuel. I don't think that fuel consumption and CO2 emissions are directly proportional, because it will depend on driving style (e.g. selecting an appropriate gear), but in rough terms the people who produce more pollution would then be paying more tax, which seems fair.
Taking another approach, maybe it would be fairer to tax people based on wear and tear. It seems reasonable that a heavier vehicle will do more damage to the road, and Wikipedia suggests that the damage is proportional to the fourth power of the axle weight, although I've found a paper from New Zealand which disputes that. If that theory is correct, the Real Cycling blog calculated that a 1000kg car would cause 10,000 times as much damage as a 100kg cyclist; if the car driver pays £100/year, the cyclist would then pay 1p/year. I agree with that blogger that I'd be willing to pay this fee if it would make drivers happy. Looking at it another way, I've lost weight since I started cycling, so me+bike (now) < me (then). Unless you want to tax pedestrians for wearing down the tarmac every time they cross the road, it doesn't really make sense to tax cyclists.
I think that the sense of unfairness applies to other debates too. For instance, the BBC published an article about child benefits in October. Quoting from that: "But he said polls suggested the idea of setting the cap at two children popular with the public, many of whom had two children and did not understand why people who do not work should have things they did not." (I'm not sure whether "he" refers to Iain Duncan Smith or Nick Robinson.) The same probably applies to the controversy about disability benefits: there's a perception that some people are living a life of luxury at other people's expense (see Guardian article).
Treating these issues as a war and demonising the other side won't really help; I think it's better to understand why people think the way they do, and try to find some common ground. That won't always be possible, because some people will flat-out refuse to listen to reason. However, I'd like to think that most people are willing to consider new information.