Speaking before Congress in the U.S. Capitol on Thursday, the Pope referenced King's famous "I Have a Dream" speech and march from Selma to Montgomery, saying he led an effort to achieve his "dream" for equal rights for African-Americans.
"That dream continues to inspire us all," the Pope told the collection of lawmakers, Cabinet members and Supreme Court justices.
He used that discussion to talk about the importance of being gracious to refugees and immigrants, speaking broadly about acceptance of others.
"We must resolve now to live as nobly and as justly as possible, as we educate new generations not to turn their back on our 'neighbors' and everything around us," the Pope said. "Building a nation calls us to recognize that we must constantly relate to others, rejecting a mindset of hostility in order to adopt one of reciprocal subsidiarity in a constant effort to do our best."
The day before, standing outside the White House and addressing President Barack Obama and thousands of listeners, Pope Francis had also brought up King as part of his call to address climate change.
"To use a telling phrase of the Rev. Martin Luther King, we can say that we have defaulted on a promissory note and now is the time to honor it," the Pope had said.
The mention of King is no accident, said Atlanta Archbishop Wilton Gregory, who was the first African-American elected president of the U.S. Conference of Catholic Bishops. Rather, it's a sign that the Pope is well aware of the increased racial tension in the United States.
"He has his finger on a number of important events and circumstances throughout the globe," Gregory said. "He's got our own issues of racial harmony on his radar. I mean, he is the pastor of the world, and so he's got to know what's going on in the world, and he got it. I think his speech is an indication that he knows what's going on in our nation."
Gregory said it would have been surprising to him had the Pope not talked about racial tensions, a subject that has gripped the nation with protests since the fatal police shooting of an unarmed 18-year-old in Ferguson, Missouri, last year.
The chairman of the Congressional Black Caucus, Rep. G.K. Butterfield, said he was sitting with other caucus members for the speech, including civil rights leader Rep. John Lewis. The North Carolina Democrat said that group was "touched" by the mention of King, and said that he raised many issues of importance to the caucus.
"He talked directly about poverty in the United States, and I think he spoke indirectly about race," Butterfield said. "I would never criticize Pope Francis for not addressing in a frontal matter, but he certainly said what needed to be said and it should give encouragement to the Black Lives Matter movement."
Butterfield also noted the Pope's discussion of young people "trapped in a hopeless maze of violence, abuse and despair" as an important acknowledgment.
"That's a recognition that the Pope understands that young African-Americans are at risk, in many areas," Butterfield said. "Of first of all, police violence, secondly not being able to get a decent job that pays a decent wage. So I think he addressed poverty directly, I think he addressed the Black Lives Matter indirectly, but appropriately."
A group of faith-based social organizers from the U.S. traveled to the Vatican this summer in advance of the Pope's trip to the country to meet with top advisers and talk about the issues behind the tensions.
"It remains an unresolved concern for our nation and the violent protests that have taken place over the last year, year and a half are an indication that it's still an unresolved issue," Gregory said. "And so I'm very grateful that he addressed it and I'm grateful that he was able to do so in such a serene way."
A call for pope to press further
But one of the faith leaders and activists that met with Pope Francis' inner circle this summer said the Pope's words left much to be desired -- and that he should have more directly taken on racial inequality.
"It's an acknowledgment of the struggle for racial justice in this country, however, I don't think the way he worded it speaks to the pain of this moment," said Bishop Dwayne Royster, executive director of Philadelphians Organized to Witness, Empower & Rebuild and a senior pastor. "When he talks about all of humanity being able to dream, the fact is that many people 50 years after the 'I Have a Dream' speech are still waiting for the dream to arrive."
Royster said the group of leaders that went to the Vatican had 20 meetings over four days with top Vatican officials, and the message they sent was, "If you're coming to America to address these issues and don't address racial oppression forthrightly, you haven't said much of anything."
But Royster said there is still an opportunity for the Pope to speak more directly on the issue, including by mentioning unrest in Ferguson and Baltimore, as he continues his trip in the U.S. He left Washington on Thursday for New York, then will end his visit in Philadelphia. There, Pope Francis will visit Independence Mall, where the only federally funded slave memorial in the U.S. is located, Royster said.
That would make a perfect backdrop for directly addressing racial tensions, he added.
"I really hope the Pope would speak more forcefully to the issue of racial justice, this is really the original sin of America," Royster said.
Gregory said it was important for the Pope to convey his message without politicizing it, focusing on harmony rather than antagonism.
Pope Francis repeatedly mentioned the "Golden Rule," urging his audience to do unto others as they would have them do unto them.
"I hope it's a reset button moment so that those who are involved in the dialogue in our own government and in municipalities in states across the nation here listen and reassess where we are and where we should be going," Gregory said.