The day before #BlackLivesMatter protesters commandeered Netroots Nation, former Rep. Barney Frank (D-Mass.) explained why the left’s 2016 candidates were not appealing to non-white voters. Frank, who considers any challenge to Hillary Clinton to be a divisive waste of money, asked liberals to consider why the supporters of Bernie Sanders seemed to be so white and comfortable.

“To some extent, and with respect to my white liberal friends in the white liberal base, these are people for whom politics is a deeply-held ideological passion,” he said. “The groups of people who have the most at stake – African Americans, Hispanics, LGBT – are much for serious for Hillary. They have got to be serious. White liberals get a psychic income for supporting Bernie Sanders, but they won’t suffer much if a Republican becomes president.”

Since the Netroots conference, Sanders has worked #BlackLivesMatter rhetoric into his speeches, and reached out to activists. But according the most recent Washington Post/ABC News poll, non-white Democratic voters give Hillary Clinton a net favorable rating of 77 points. Sanders’ net rating is just 19 points. Some of that is a function of Sanders lower name ID, but 23 percent of non-white voters view Sanders negatively – and only 9 percent view Clinton that way.

Sanders' supporters, who number among the most intense partisans in the primary, have not helped close the gap. From the start of the Netroots interruption, some of them have chastised activists for making a loud, risk-free protest against a politician who should be their ally. David Atkins, a political strategist who was in the room for the interruption, went on a tweetstorm about how the activists had discredited the movement.

David Dayen, a writer and blogger who covered the conference for Salon and The New Republic, asked whether Sanders was being denied some credit for decades of activism. (In his TNR coverage, Dayen argued that Sanders nonetheless "failed [his] #BlackLivesMatter test.")

The left-wing writer Matt Bruenig added to the backlash by annotating an interview with Tia Oso, the Phoenix activist who led the disruption. Oso chastised Sanders for discussing poverty "without the context of white supremacy." Bruenig found her critique to be incoherent.

"Does Bernie Sanders really want to talk about job creation?" he asked. "It’s all he talks about. The fact that job creation and similar economic topics is mostly what he talks about is the supposed racial critique!"

They surely didn't intend to, but the critics talked right around the protesters. The best way of understanding what the fuss was about is to watch one of the many videos shot from the thick of the Netroots protest. At 8:47, in a video uploaded by Andrew Davey, you can hear protesters demand that Sanders explain how he'll ameliorate racism in America. You can watch Sanders give what he thinks is complete answer -- and be denounced.

"We're going to transform the economics in America so that we create millions of decent-paying jobs," said Sanders in the clip. "We're going to make tuition at public colleges free."

"Jobs and college don't stop the police from killing me!" said a woman in the crowd, audible in the room but not on official videos of the event. "Jobs and college don't stop the police from killing me!"

Sanders plowed forward. "We're going to reform our trade policy so that corporate America invests in this country, and not low-income countries around the world," he said.

"Trade policy doesn't stop the police from killing me!" said the woman.

Inside the room, there were many, many more chants like that. In the conversations that spilled into the hall, activist after activist asked why white liberals were so insistent on talking about poverty before discussing white privilege. This Week in Blackness host Elon James White, engaged in a running dialogue, in person and on Twitter, with the white progressives who did not seem to get it.

He and Oso retweeted plenty of jokes about the disconnect. On the surface, the #BernieSoBlack hashtag -- mockery of the white liberals who said that Sanders was not getting credit for years of civil rights activists --was a jibe at Sanders. As it grew in popularity, the hashtag became a joke at the expense of white progressives.

Those tweets go some way toward explaining why white progressives are getting friendly fire when they praise Sanders. The white progressives don't disagree about racism (it's institutional) or white privilege (it's a problem). But many, like Sanders, think the gulf in wealth and opportunity between white Americans and non-white Americans can be fixed by "transforming the economics" of the country. Many black progressives say that "white supremacy" has to be the center of the discussion -- or there is no real discussion at all.

“What I saw at the Netroots Nation revealed, not so much an interracial divide as much as I witnessed an intra-racial, ideological divide between and among white progressives,” said Kimberly Ellis, an activist who co-founded #AskASista, a popular perennial Netroots panel about black life and politics. “It's more dramatic to say or think, ‘#BlackLivesMatter disrupts white progressive Bernie Sanders’ but it's far more accurate to state that Elizabeth Warren's ideology is more intersectional, gendered and overall even more progressive than Bernie Sanders'. The suggestion that #BlackLivesMatter protestors don't understand race and class is ridiculous. We have a fundamental disagreement with Bernie Sanders that racism is somehow an offshoot from economic exploitation when the reality is that race and class in America are inextricably linked to the rise of capitalism in this country to the industrial revolution.”

Sen. Bernie Sanders (I-Vt.), a White House contender in 2016, is known for his stances on budget issues and war. Here are his takes on Obamacare, Social Security and more. (Julie Percha/The Washington Post)