“Are y’all done hearing from people who do not want change?” said Glenn Foster, an organizer. “So what are we going to do? We are going to tear that motherf—er down! And if you don’t like it, you don’t like it.”

That brought an angry response from Marcia Cole, a re-enactor who had arrived in costume as Charlotte Scott, the freed slave whose $5 donation in the wake of Lincoln’s assassination started the campaign to raise money for what was then known as the Freedmen’s Memorial Monument.

Ms. Cole said the image of the kneeling slave was one of promise. “His chains are broken; he knows he’s free,” she said, adding, of Charlotte Scott, “You have no right to besmirch her legacy.”