If energy generation had no side effects, then you'd be right, maybe it shouldn't be taxed.

But energy generation does have side effects, which are a drain on the general economy. Environmental cleanup is not productive, except to the small degree that private companies make a profit from it; in terms of the economy as a whole, it's money spent on fixing something that could have been used more profitably elsewhere. Nor is remedial health care a productive use of money.

Consider the other main use of gas taxes: Paying for road maintenance and construction. If you don't own a car and instead use public transit, why should you pay for roads that you don't use? If you use a car only rarely, for things like trips to the grocery store, why should you pay the same amount for the roads as the guy driving a compensatory Hummer a couple of hundred commute miles every day?

I'm surprised the RightWingers and Libertarians have a problem with this. It's really no different from user fees, which were huge among conservatives a few years ago as the first step toward privatizing as much government as possible. They touted user fees using exactly the same arguments: Make people who use something pay for it, and don't stick everybody else with the bill.