2) That's his risk to take when he's on the race track. Not on a public road. The harm he has potential to do increases, and he has no right to take that decision for everybody else on the road.
Actually, that's not true. The expected severity of an accident goes up but the chance of an accident goes down. This is primarily because the faster you go, the less time you are on the road and accident risk correlates much more strongly with time on the road than it does with speed. In most realistic scenarios, he poses less risk to others because he's not on the road for as long. (Obviously, this isn't true if he was going so fast he wasn't in control.)
I'm not certain that I agree that overall risk decreases with an increase in speed. Can you point me to an analysis that demonstrates this? I suspect you are mistaken on this point.
3) More fuel burned, more pollution. WTF does cost have to do with anything? People nearby breathe in more pollution, that's harm. And if you agree with +90% of the climate scientists you also contribute to global warming, admittedly not by much though. Still harmful to the environment.
Right, but to figure out if that's a *net* harm you have to balance it against the net gain to society of his speeding. If you don't see why this is so, imagine if everyone drove at 10 miles per hour and think about what effect that would have on the economy.
But society has already determined the balance they want. They elected representatives who chose a speed limit that society feels is fast enough to provide the necessary benefit, while slow enough to keep risk and pollution acceptable.
Would you support a national 45 mile per hour speed limit? I mean, look at all the benefits it should have -- less risk, less fuel burned, all things you seem to think are good. If you think speed limits are set to some kind of scientifically optimal value, I have a bridge to sell you.
While I may not support a 45 mile per hour limit, I may also not support a 55 mile an hour limit. As such I can choose my representatives based on their stand on this issue. If enough of society is willing to accept a 45 mile an hour limit for those benefits, then the law will change, and I'll be held to the new rules regardless of personal preference for speed limits. They don't need to be scientifically optimal, they simply need to be acceptable by society.