In 2010, Automobile accidents claimed 32,885 lives. Is being able to travel at 70 miles per hour worth 32,000 lives per year?
That is a good question. Automobiles impose costs on society and therefore should be taxed at a punitive rate to discourage excessive use. Here in Singapore the costs of purchasing a Honda Civic are in the neighborhood of USD$150,000. Part of this is tax. All cars are taxed at 200%. There is also purchase of entitlement to own an automobile (~$30,000). There is also purchase of the entitlement to drive which is about $20,000 per year if you want to be able to drive during peak hours (much cheaper for an off peak license).
These are excellent moves. Cars cause external harm and therefore call for punitive taxation.
Guns should also be heavily taxed (e.g. there is one paper which suggests that $600/gun is an appropriate tax rate).
The problem with this is only the rich can afford to defend themselves. people living in low income areas would not only be the most numerous demographic, but also the most likely to need a firearm for self defense. If you need to get somewhere and don't own a car, you can carpool, get on a bus, or call a taxi. If you are being attacked and you don't have a gun you are a victim, and if the police show up it most of the time it will only be to fill out paperwork if you are lucky enough to be alive.