BOSTON — When President Biden met with the prince of Wales on Friday at Boston’s John F. Kennedy Presidential Library, they were met by more than 100 protesters, not the genial crowd that usually forms for the two men. 

People held signs denouncing the president for signing a bill that imposed a contract on America’s railroad workers after a majority of employees voted against ratifying the deal. “It’s terrible,” one of the picketers, Joe Kebartas, said. “These people should have a half-decent living wage with sick days.”

Some of the signs read: “Please support sick days for workers,” “Without the right to strike, workers have no rights,” and “Paid leave for railroad workers.” As the president exited his limousine, he was met by chants of, “Biden is a scab.”

One organizer led the group in a series of call-and-response chants, including, “When railway unions are under attack, what do we do? Stand up, fight back.” Another popular chant was “Get up, get down, Boston is a union town.”

A union railroad worker, Nick Wurst, one of the protest’s organizers, told the Sun that the picketers wanted to show the president that he was wrong to enforce the contract.

“We’re out here today with supporters to make it clear that we oppose the deal that’s been forced down our throats by an act of Congress and that’s now been signed by President Biden,” Mr. Wurst, who was wearing his union jacket, said.

Asked about what happens next, he was defiant: “We have to start organizing immediately. This flight isn’t over just because someone signed an agreement.”

Families of union workers also appeared. “Rail workers need time off. We must guarantee the two-person staffing requirement. End the policy of equipping workers with minimum staff levels and shoddy equipment,” the wife of a union rail worker said in a speech to the group.

It wasn’t just rail workers who came to the protest. Other labor groups included the trade unions, the culinary unions, and members of the Harvard Graduate Student Union. The Democratic Socialists of America group was also present. 

A member of the Harvard Graduate Student Union, Andrew Bergman, said it was important to be here to support the rail workers. “The ability to practice worker democracy through voting on your own contract and then being able to go on strike,” Mr. Bergman said, “is absolutely critical.”

“When Biden and Congress — Democrats and Republicans — quash that, it’s a sign we’re heading absolutely in the wrong direction,” he added. 

The protesters did more than just share their anger at the president: They also took aim at some of the most left-wing members of Congress. “AOC tweeted about how she supported workers the same day she voted for this bill,” one speaker said, referring to Representative Alexandria Ocasio-Cortez. The crowd then booed  loudly. 

After Mr. Biden’s meeting with Prince William, the president was driven a few miles to IBEW Local 103, where he participated in a phonebank with members on behalf of Senator Warnock, who faces a runoff vote against Herschel Walker next week in Georgia. Mr. Biden was due to then return to the JFK Library for a Warnock fundraiser.

Some union protesters said they were planning to stay outside the event until the president leaves for Washington later Friday. 

Mr. Biden has long styled himself as “Middle Class Joe” and “the most pro-union president in history,” but his actions have many workers feeling betrayed. 

“It shows a lot about where his loyalties lie. His loyalties lie with corporate America,” said Mr. Wurst. “He wants to protect the profits of the corporations that fund his campaign and fund his party.”

The anger on display at the event was palpable. Many speakers hurled expletives at the president as he entered the library. Many union members and their families — a demographic Mr. Biden won by 17 points in 2020 — feel betrayed. 

Mr. Wurst had an optimism about him, however: “This fight’s not over.”