Well, if you’re going to base election strategy on the premise that Americans are just sheep, then all bets are off. You think those same “sheep” are going to vote for someone that the same media call a “Socialist” a billion times?
Your litmus test cuts out everyone except Bernie. Other litmus tests other Democrats might have – POC, woman, not old, calm demeanor, not a socialist – will cut out Bernie. Fortunately, the actual way the party chooses candidates is by primaries, not peremptory challenges, and those determine things like electability through actual elections.
Sanders supporters (and I’m one) don’t do him any favors by channeling so much energy into angrily rubbishing all the other candidates at this time, not to mention the electorate. I’m pretty sure Bernie wouldn’t agree with you that Americans, even Trump supporters, are sheep.