Jamaal T. Bailey, a state senator who represents the Bronx and Westchester and considers Mr. Heastie his political mentor, said Democrats should focus on party unity, citing lyrics from the Jay-Z song “Family Feud.” “Nobody wins when the family feuds,” he said. “What’s better than one Democratic majority? Two.”

Even black activists who have been heavily involved with the new activist groups warned that certain voices should be careful not to drown out others.

Sherese Jackson, who until recently was the only nonwhite board member of Indivisible Nation BK, an activist group in Brooklyn formed after 2016, said the group often discusses how to increase diversity. But the discussions had yet to turn into real change.

“It is definitely a struggle as a woman of a color,” she said, “feeling 100 percent safe in a mostly white, progressive world.”

Events such as the protest against Mr. Heastie, even if well intentioned, could further deter nonwhite people from joining, she said.

“The visual alone — I could see how that could come across to people, and it could be a turnoff,” Ms. Jackson said. “This does not help the trust factor.”