Be careful what you ask for
I love this internet meme that the purest of the pure Bernie backers can't vote for "the lesser evil" (i.e., Hillary Clinton).
Not only is it a religious argument (where the vote is a sacrament, and it is defiled by being used for the benefit of someone who is not pure of ideology), it's an ahistorical argument. Many of the same people who insist on not supporting "the lesser evil" point to LBJ as an example of a politician who overcame evil, proving it can be done.
LBJ, of course, passed the Civil Rights Act because JFK was assassinated. He deliberately and publicly linked it to JFK's death. But it was also the result of Truman integrating the armed forces, and the push for integration that started among African Americans after World War II, a push that lead to the creation of the Southern Christian Leadership Conference, the rise of Dr. King, a civil rights act passed under Eisenhower (the one Kennedy wanted to amend and extend), the Montgomery Bus Boycott, and the March on Washington (which we forget was in 1963).
LBJ, in other words, didn't act in a vacuum, or completely cut off from history. Even the Voting Rights Act, which was pure LBJ and was finally the implementation of the 15th Amendment, didn't happen without the march from Selma to Montgomery, and other actions by Dr. King and his associates. LBJ wasn't a single brave white man (like John Wayne in the movies) saving the black man from ignominy (again, like John Wayne in his later movies, where it was acceptable to treat Indians not as savages, but as oppressed people. Oppressed by people like John Wayne's characters in the movies, but no matter: white man must save brown man. Always.), but set that aside too (along with all the African Americans who wouldn't vote for Bernie. His most ardent supporters do.) He didn't act alone, and he didn't act despite the prevailing sentiments of the country.
And the final irony is that LBJ didn't run for re-election, the first time in modern American history, because of the Democrats who despised him over Vietnam. Which quest for purity of ideology and in the name of "no lesser evil!", gave us 5 years of Richard Nixon (would have been 8, but for Watergate).
So, yeah, let's refuse to vote for the "lesser evil." What could go wrong?