Bernie Sanders is an unlikely phenomenon.

He is attracting massive crowds. His message of economic populism has infused his insurgent candidacy with an Obama-like level of electoral enthusiasm, only his base isn’t as broad (As CNN put it last month: “A June CNN/ORC poll showed just 2 percent of black Democrats supporting Sanders, a figure that has remained unchanged since February. Among nonwhite voters overall, Sanders polls at 9 percent, compared to Hillary Clinton’s 61 percent.”)

Still, Sanders’ candidacy has become something of a movement. But two times in recent weeks, Sanders’ appearances at events have been disrupted by supporters of another movement: Black Lives Matter.

The most recent disruption came at an event in Seattle last weekend, where two female Black Lives Matter supporters prevented Sanders from speaking. Sanders has responded well to the most recent disruption, issuing a thorough and utterly impressive “Racial Justice” agenda that liberally quotes from the Rev. Dr. Martin Luther King, Jr. and even includes the line: “We need a societal transformation to make it clear that black lives matter, and racism cannot be accepted in a civilized country.” Further reiterating his commitment, he said at a rally in Los Angeles, “There is no president that will fight harder to end institutional racism.”

But, not all of Sanders’ supporters could muster his magnanimity. Some were outraged. The protesters were seen as disrespectful and indecorous. Sanders was not only seen as a bad target, he was one of the worst targets because he has a long history of civil rights activism, including participating in the 1963 March on Washington and hearing the King himself.

Some irritation was understandable. But some went too far, repaying what they saw as rudeness with what I saw as crudeness. The conspiracy theories began to swirl and the invectives — including some racist and sexist ones — began to flow. It exposed something that isn’t discussed nearly enough: a racial friction on the left.

There were sweeping condemnations of the Black Lives Matter movement itself, a sense that benevolence had been rebuffed, that allies had been alienated. Some people sympathetic to the protesters responded by making a King reference of their own, pointing to this passage from his 1963 “Letter from a Birmingham Jail”:

“I must confess that over the past few years I have been gravely disappointed with the white moderate. I have almost reached the regrettable conclusion that the Negro’s great stumbling block in his stride toward freedom is not the White Citizen’s Counciler or the Ku Klux Klanner, but the white moderate, who is more devoted to ‘order’ than to justice; who prefers a negative peace which is the absence of tension to a positive peace which is the presence of justice; who constantly says: ‘I agree with you in the goal you seek, but I cannot agree with your methods of direct action’; who paternalistically believes he can set the timetable for another man’s freedom; who lives by a mythical concept of time and who constantly advises the Negro to wait for a ‘more convenient season.’ Shallow understanding from people of good will is more frustrating than absolute misunderstanding from people of ill will. Lukewarm acceptance is much more bewildering than outright rejection.”

It all quickly became an arms race of overheated accusations.

But, I must say that I, too, found some of the responses to the protesters troubling.

First, some people said that the disruption had caused the movement to lose their support. This seemed strange and extreme to me. How fragile must your support for black lives have been if a rally’s disruption caused it to crumble?

Secondly, centering one’s disapproval of the protesters on white allegiance, rather than black agency, seems to me a kind of cultural narcissism.

The movement, to my mind, isn’t a plea for pity, or appeal to comity, but an exercise in personal and collective advocacy by an oppressed people.

It says to America: You will not dictate the parameters of my expression; you will not assign the grammar of my pain; you will not tell me how I should feel. For these young activists, it’s not ideological but existential; it’s not about a political field but a battlefield, one from which they cannot escape, one on which their very bodies are marked and threatened with destruction.

This is not an esoteric, intellectual debate about best practices, but quite literally a flesh and blood struggle for equal access to liberty and longevity.

In this movement exists a kind of urgency that only proximity to terror can produce, and yes, that urgency can be extreme and discomforting, because it must be. The sedative of all normalcies and niceties are the enemies so long as lives are in danger. The movement is revolutionary out of necessity. Some people operating under those auspices will inevitably employ tactics and select targets with which you disagree. That too is understandable.

But, those who object must be careful not to become “more devoted to ‘order’ than to justice.”