http://www.pewresearch.org/fact-tank/2017/05/12/black-voter-turnout-fell-in-2016-even-as-a-record-number-of-americans-cast-ballots/ I may come back later to respond to your last paragraph. Where in this piece do you read Coates "yelling at white people"?The reason working class black voters aren't part of the conversation is because they did what was expected.
If black voters want the Democrats to pay attention, stop with the blind support. Vote third party.
I'm not sure not voting is enough (particularly when the result is a Trump presidency). As for him yelling at white people, that was like half of the piece. He spends much of it talking about how Trump voters could only have voted for him because they're racist, and how the rest of us talk about white working class voters because we're racist.