The commenter on the panel on Diane Rehm this morning said it: Sanders can't win large numbers of votes in states with large numbers of African Americans in them. Sanders' support is largely young and white, and that is a racial as well as generational divide. Those who are "fed up" and white should matter; and the panel is going on to casually talk about voters who like Sanders, and like Trump, and they never notice because it's not about race because it's never about race.
And even our "liberals" aren't handling that very well. Even millennials are easily prompted on comment boards to rail against "racism" that they perceive is being stirred up where there wasn't any racial tension before. Because it's not about race, because it's never about race. And when it is about race, it's because you're doing something wrong; to white people.