The Rev Dr William Barber’s arrival in the world was full of portent. He was born on 30 August 1963, two days after Martin Luther King’s I Have a Dream speech at the March on Washington, and two weeks before a church bombing in Birmingham, Alabama, killed four African American girls. When Barber was three months old, President John F Kennedy was assassinated in Dallas.

“My parents were asking, ‘What kind of America have we brought this child into in the 20th century, where it could be blown up sitting in a church for Sunday school?’” Barber recalls. “One day in North Carolina, when they were turning back voting rights and healthcare and attacking the gay community and Latinos, I met my mom and she had a tear in her eye. She says, ‘I never thought that I would have a child 50 years ago and that child would grow up and end up having to fight to hold on to some of the things that we tried to win.’ And then she looked at me and said: ‘But you’d better fight.’”

His willingness to do so, from the pulpit and on the streets with rare eloquence, passion and clarity that cuts through the noise of cable news and social media, has seen Barber compared to King as America’s new apostle of nonviolent resistance. He is co-chair of The Poor People’s Campaign: A National Call for Moral Revival, a grassroots movement planning six weeks of civil disobedience this spring to “save America’s soul”. It evokes King’s own poor people’s campaign, which petered out after he was gunned down 50 years ago.

That trauma, too, touched Barber in infancy. He recalls: “I would have this picture in my mind of my mother just crying and bent over. She was looking at the TV and my father came in and was weeping. I was about four, almost five, and I guess it was so traumatic that I still can’t remember but my mother told me later that was when Dr King got shot and it came across the TV. I can even sometimes now just hear her screaming.”

Asked what King means to him half a century later, Barber, pastor of Greenleaf Christian church in Goldsboro, North Carolina, speaks for 14 minutes with barely an “um” or an “ah” or a pause to draw breath. He expresses admiration for the civil rights leader’s commitment to “interlocking injustices”, a model for the intersectionality of his own poor people’s campaign. “You cannot separate systemic racism from systemic poverty from ecological devastation from the war economy from the distorted moral narrative of Christian nationalism that tries to suggest those issues I just mentioned are not moral issues, and the only moral issues are things like being against gay people and against abortion and for prayer in school.”

Barber, 54, also praises King for his “loving radicalism”. At Riverside church in New York in April 1967, he spoke out against the Vietnam war, describing the US government as “the greatest purveyor of violence in the world today”. His final sermon, which he never got to preach, was to be entitled Why America May Go to Hell. But this edgier, confrontational King, who lost friends and alienated people, tends to be forgotten in today’s rush to sanctify, sanitise and simplify in ways that would make him uncomfortable, Barber argues.

“The powers that be want to isolate him so that we almost make Dr King the Messiah that is dead rather than recognising that he didn’t even like that,” he says. “He understood that the movement was about us all. The powers that be want to have us stuck in I Have a Dream – that part of a speech – and act almost as though Dr King didn’t say anything else. Many times, not just the powers that be but even some people in the movement, do not read in depth and listen in depth to Dr King.”

Facebook Twitter Pinterest Martin Luther King speaking to his congregation at Ebenezer Baptist church on 30 April 1967. Photograph: Anonymous/Associated Press

On one occasion, Barber recalls, he was invited to speak at a King-themed breakfast under the theme “Where do we go from here?” – the title of King’s final book, which Barber read by way of preparation. “I talked about what Dr King meant and the organisers of the breakfast got mad. They said to me: ‘We didn’t invite you here to talk about those things. We invited you here to talk about love and reconciliation.’ I said: ‘I did. I talked about it the King tradition because there can be no reconciliation until there’s conciliation and there can be no conciliation until there’s trust, and I pulled the book out of my bag and said, ‘You chose the title but didn’t read the book.’”

We have commemorations of his life rather than a commitment to his actions William Barber

He continues: “We have commemorations of his life rather than a commitment to his actions and what that means in almost every city is corporations and groups will sponsor a breakfast on the King birthday but will not change their policies and create a living wage. We we go to the Edmund Pettus Bridge [in Selma] and we commemorate what they did marching on Bloody Sunday but we don’t march into the Congress and demand that the Voting Rights Act be fixed. Even when we go to Memphis, the garbage workers [whom King championed] still don’t earn a living wage.”

Barber – who has himself endured death threats – will travel to Memphis for the 50th anniversary of King’s death, marked by a Where Do We Go From Here? symposium and commemorative ceremony from 2 to 4 April. But he believes mere remembrance is not enough. “The only thing you can do with the assassination of a prophet to truly honour them is to reach down in the blood, pick up the baton and carry it the next mile of the way.

“It is not merely to preach the themes of Dr King – it is to live them out. So if at the end of his life he was organising poor people, that’s what we ought to be doing. If at the end of his life he was demanding a Marshall Plan for the poor, demanding living wages, demanding guaranteed income for the poor and disabled among us, demanding healthcare, and if he was willing to not only demand it from the pulpit but to get in the street with the poor then we should do no less than that, not just because it’s the 50th year of his assassination but because 50 years later we have 140 million poor people in this country.”

If King had survived he would now be 89, having witnessed the elections of both Barack Obama and Donald Trump and fresh setbacks to healthcare and voting rights. Barber reflects: “If Dr King was alive today, I don’t think he would be wasting time so much saying, ‘Oh, you all went backwards.’ First of all, he would have been working all of this time and we probably wouldn’t be in some of the places where we are. But even if he was alive he would be engaged, I believe, in saying we have got to fight to restore this Voting Rights Act, we have to fight against this poverty. He would be challenging this business of giving tax reform to the wealthiest at a tune of three trillion dollars which is the largest transfer of wealth we’ve seen since the wealth that was transferred from slaves to the slave owners’ aristocracy.

“He wouldn’t be just talking about Trump, just like he didn’t just talk about [former Alabama governor] George Wallace. He would talk to us about the systems that created a Trump or created a George Wallace and challenging those systems. He would be doing a deep analysis and that’s what we’re trying to do. Like any human he could be disappointing, had his faults and failures and all those things, but he would be turning that disappointment into: how now do we deal with this, how do we challenge it? How do we deal hope in the midst of the despair, how do we bring people together? He would say let’s organise, let’s speak prophetically, let’s challenge America with our deepest moral and religious principles. I know that’s the only way we can truly pay homage to him again.”