On the one hand, Lessig relies (correctly) on the fact that the Constitution places no restrictions on how electors vote and that it was expected that they would be citizens exercising judgement.
On the other hand, he disagrees with a very fundamental feature of the Constitution -- that states, by the fact they are states, have power beyond just the mass of their population. This is directly evidenced in the Constitution as it defines how the Electoral College and Senate work. The Founders felt so strongly that each state have an equal vote in the Senate independent of the population of the state that the ONLY thing that can't be amended in the Constitution with approval of ¾ of the states (NO state can lose equal suffrage in the Senate without approval of that state).
It seems quite odd to rely on the Constitution for one argument and then completely dismiss one of its most fundamental concepts that protected the less populous states from being run roughshod over at the Federal level by the more populous states. One might go so far as to label such a viewpoint as hypocritical.