At a march in mid-December organized by Al Sharpton’s National Action Network in Washington D.C., organizers rushed the stage and claimed that the old guard was attempting to hijack the nascent Black Lives Matter movement away from its founders.

“This movement was started by the young people,” Johnetta Elzie, a key organizer from St. Louis, said to the raucous crowd. “There should be young people all over this stage.”

It was one of the most visible examples of the clash between the old, signified by Sharpton, and the new, represented by grassroots groups who emerged from Ferguson and New York after the Michael Brown and Eric Garner grand jury decisions.

Sharpton has been extremely sensitive to this criticism. “Oh, you young and hip, you’re full of fire. You’re the new face,” he sneered at a recent gathering at the headquarters of NAN in Harlem. “All that the stuff that they know will titillate your ears. That’s what a pimp says to a ho.”

At an MLK Day march in Harlem, the division between the old and the new was quieter but no less pronounced.

On Luxembourg Street, three cops stood behind a barricade, just a few feet away from a thousand protesters. One of the two female officers, brown skinned with accentuated eyebrows, plucked lint from the uniform of her stocky, white male colleague; they all laughed.

Meanwhile, a dozen or so protesters began to veer from a universal chant—one about justice being lost until it is found—to a more abrasive one: “How do you spell racist? N-Y-P-D.” It’s the same kind of chant Mayor Bill de Blasio called “hateful” and an “attempt to divide this city in a time when we need to come together” a week after two detectives were fatally shot in their squad car in Brooklyn. Immediately the three officers stiffened their backs and softened their smiles.

Minutes later, dozens of members of a group called Justice League NYC stormed past the officers on the sidewalk, led by some of its key staffers, with Councilmember Jumaane Williams at their side.

Seeing the group of well-groomed activists and politicians stroll by, the three officers relaxed and dropped their hands from their waists. The police seemed to know that for all the demonstrators’ bluster, it was going to be an uneventful day.

Read More The Fight For The Soul Of The Black Lives Matter Movement: Gothamist.