During the election season, Bill de Blasio was often painted by conservatives as a leftist radical. But at his inauguration today, it was not Mr. de Blasio who dropped the most aggressive lines, but the first two speakers at the event.

In particular, Rev. Fred Lucas Jr., who was among several chaplains representing the city’s uniformed workers, surprised many observers by comparing the five boroughs to a “plantation.”

“Let the plantation called New York City be the city of God, a city set upon the hill, a light shining in darkness,” he declared. “Elevate our valleys. Make low our mountains. Make our crooked places straight and our rough places smooth. Oh God, oh God, oh God, break every chain, break every chain, break every chain.”

Mr. Lucas had several additional references to slavery in his short address, citing shackles, bondage, auction blocks, the Emancipation Proclamation, Civil War and Reconstruction Era.

“Oh God, on this first day of January–the anniversary of the first Emancipation Proclamation–sound forth the trumpets of heaven proclaiming a new Emancipation Proclamation in New York City,” he invoked. “From your divine leadership, emancipate every New Yorker from the shackles of fear, futility and frustration … Oh God, end the civil wars and usher in a new Reconstruction Era that builds upon the many successes and achievements of yesterday while proclaiming the beginning of a new beginning.”

The speaker before Mr. Lucas, civil rights activist Harry Belafonte, was also blunt as he discussed racial tensions and injustices cemented by government policies. (Mr. Belafonte, of course, is not known to be a bashful speaker; during the campaign, he caused controversy after comparing the billionaire Koch brothers to the KKK.)

“New York, alarmingly, plays a tragic role in the fact that our nation has the largest prison population in the world. Much of that problem stems from issues of race perpetuated by the depth of human indifference to poverty. Changing the stop-and-frisk law is … only the tip of the iceberg in fixing our deeply Dickensian justice system,” he argued, referencing the controversial police tactic Mr. de Blasio has vowed to overhaul.

But Mr. Belafonte, one of Mr. de Blasio’s endorsers in the campaign, said the new mayor was the right man to help undo these systemic injustices.

“We have seen America wrestle with her conscience. We have seen her struggle to become her better self. I think the solution to what most people want America to become resides here in New York. We can become America’s DNA for the future,” he said. “Bill de Blasio gives New York another opportunity to open the door of possibilities.”

Mr. Belafonte concluded, “We New Yorkers must not let him fail.”