I would call the writer of the article a Real American Liberal. He is recognising the mistakes liberals, including perhaps himself, are making and recognising in addition to that the reasons why Trump got elected. And I think he is pondering, like many another person I imagine, what Real Liberals need to do to get back the support of those they've lost.
The quote you give, ankers, is the essence of the problem. People who voted for Trump are looked down on and spoken of as he says (rednecks, stupid, trailer trash, etc) and, as Hillary Clinton said, "deplorable". Hardly a vote winning strategy. But more than that, it's actually very sad that politicians and media commentators sneer at people in this way, and no bloody wonder someone like Trump, whom they don't see as sneering at them, got voted in instead.
The same sneering attitude exists here in the UK: the "people don't know what's good for them" attitude, and "they should take heed of the experts". That last always makes me laugh because experts' opinions and pronouncements disagree just as much as anyone else's.