Civil rights leaders reacted with fury to the move by Republicans to silence Elizabeth Warren as she was in mid-flow on the floor of the US Senate, reading out a 1986 letter from one of the titans of the struggle for race equality, the late Coretta Scott King.

King’s friends and fellow members of the movement for equal rights, in which she had played a prominent role alongside her husband Martin Luther King, responded with anger to the action of the Republican majority leader, Mitch McConnell. He cut Warren off mid-sentence, claiming that by quoting King’s words the Democratic senator had broken a Senate prohibition on members impugning the conduct of their peers.

The instant backlash from civil rights figures was spearheaded by the daughter of Coretta and Martin Luther King, Dr Bernice King, who within hours of the Senate drama unleashed blistering criticism of the direction taken by the Republican party. Setting out on Facebook a 10-point program for how to resist the new Republican stranglehold on White House, Senate and House of Representatives, she reserved her most pointed words for Donald Trump, though without naming him, since point one of her manifesto was: “Don’t use his name; EVER.”

She added, “45 will do” – a reference to Trump’s status as 45th president of the United States.

Rev Jesse Jackson, who was present at the Lorraine Motel in Memphis on 4 April 1968 when Martin Luther King was assassinated, called the abrupt termination of the reading of Coretta Scott King’s letter a “moral disgrace”. Jackson told the Guardian that the move was “beneath the dignity of the American dream”.

The silencing of Warren happened at a confirmation hearing for Jeff Sessions, Trump’s pick for US attorney general and one of the most contentious of his cabinet nominees. She was reading from a letter that Coretta Scott King had written in 1986 in which the late civil rights leader opposed in very strong terms the earlier nomination of Sessions for a federal judgeship for the southern district of his home state, Alabama.

King wrote in the letter that Sessions was unsuitable for elevation to the courts because he had “used the awesome powers of his office in a shabby attempt to intimidate and frighten elderly black voters”.

Jackson said that by halting Warren’s reading, McConnell had exposed the kinship between Trump and the Republican party. “Just as Sessions sought to silence Dr King’s movement for the protected right to vote, McConnell last night sought to silence Coretta Scott King’s letter – it’s a consistent pattern.”

Rev Dr Barbara Reynolds, a close friend of Coretta Scott King who co-authored her memoir, My Life, My Love, My Legacy, said she was “appalled and upset” by what had happened. It was all the more disturbing, Reynolds said, given King’s specific and personal criticism of Sessions in the letter.

“At the time she wrote the letter, Sessions was working as a prosecutor and the people he was fighting were people she had grown up with outside Marion, in Alabama. He was prosecuting black people trying to help other blacks register to vote – and that’s what the civil rights movement was all about.”

Reynolds said that King had been so opposed to the idea of Sessions sitting in judgment in a federal court because “she didn’t want to go back to the life they led before they won the right to vote. Her family’s lumber mill was burnt down by white terrorists and there was nothing they could do about it precisely because they didn’t have the right to vote.”

She added: “Even now, in 2017, they are silencing Coretta Scott King. They won’t let her speak now, but her words still matter.”

In the book they wrote together, King says: “I am counting on the next generation to pick up the still broken pieces of society and continue the struggle against poverty, greed and power that Martin and I gave our lives to. Freedom is never really won; you have to earn it and fight for it in every generation.”

Sessions was rejected for the judge’s position in 1986. The judiciary committee of the US Senate voted his nomination down after the hearing was told that he had been accused of using the N-word to describe a black official in Alabama.

He is expected to be confirmed as attorney general by the Senate on Wednesday evening.