Chomsky's argument is fundamentally unsound but there is an even more damaging criticism of it: it is built on a false proposition: that LEV is itself a sound principle. We cannot vote on a basis of assumption concerning consequences - where would such an approach end? Where is the proof or likelihood of good outcome to justify such a strategy? Should I say, as Chomsky does, that Clinton will cause less damage to certain groups than will Trump? Or should I argue the reverse and claim that Trump's election will constitute a good? I may wish to thoroughly befuddle myself and argue that a short term Trump Presidency may lead to a better long-term future, a reformation in the Democratic Party which has become corrupted, or that abstinence from voting may serve to bring about reform of the US system in spite of short-term negative effects. There is a simpler way, without fear of that "moral self-aggrandizement" which Chomsky warns us of in the hope of securing our acquiescence to his weak argument: we must remember that in most democratic countries we may choose to vote or not; we should therefore vote with precepts which appear to us sound, we should try to do so ethically always, taking account not only of ourselves, nor should we vote on the basis of a particular outcome, favourable or otherwise. Voting is a personal matter; no-one should vote for either candidate unless their internal belief systems dictate strongly that they do so. It is misguided to recommend LEV as a basis for voting and it compounds the many problems with representative democracy as well as causing an individual to become complicit in an evil decision/consequence. LEV is not appropriate as a principle for democratic elections: it is at best a personal choice, it is not an ethical choice per se; it is not dependent on first principles and it is not a proper application of LEV because of its complexity of decision and the availability of other moral choices.
Chomsky's argument is thus an attempt to square the unvirtuous circle and fails on many counts. The road to Hell may be paved with good intentions, but Heaven is certainly not achieved by following the path of the Lesser of Two Evils.