“It was Mill who popularized the idea of raising taxes on landowners only after first compensating them, thus buying the right to tax them. It was a selective scruple: neither Mill nor anyone, to my knowledge, ever proposed compensating workers, consumers, or the owners of capital before taxing them. It was something of a red herring, because it assured that net revenues would be about zero. It simply gave debaters something to chew on while precluding meaningful action.”