By SCOTT SHANE
“We must pledge ourselves to support those brave men and women who this very moment are carrying forth the struggle against British imperialism in the streets of Belfast and Derry,” Mr. King told a pro-I.R.A. rally on Long Island, where he was serving as Nassau County comptroller, in 1982. Three years later he declared, “If civilians are killed in an attack on a military installation, it is certainly regrettable, but I will not morally blame the I.R.A. for it.”
As Mr. King, a Republican, rose as a Long Island politician in the 1980s, benefiting from strong Irish-American support, the I.R.A. was carrying out a bloody campaign of bombing and sniping, targeting the British Army, Protestant paramilitaries and sometimes pubs and other civilian gathering spots. His statements, along with his close ties to key figures in the military and political wings of the I.R.A., drew the attention of British and American authorities.
A judge in Belfast threw him out of an I.R.A. murder trial, calling him an “obvious collaborator,” said Ed Moloney, an Irish journalist and author of “A Secret History of the I.R.A.” In 1984, Mr. King complained that the Secret Service had investigated him as a “security risk,” Mr. Moloney said.
In later years, by all accounts, Mr. King became an important go-between in talks that led to peace in Northern Ireland, drawing on his personal contacts with leaders of I.R.A.’s political wing, Sinn Fein, and winning plaudits from both Bill Clinton and Tony Blair, the former president and the British prime minister.
But as Mr. King, 66, prepares to preside Thursday as chairman of the House Homeland Security Committee at the first of a series of hearings on Muslim radicalization, his pro-I.R.A. past gives his many critics an obvious opening. The congressman’s assertions that 85 percent of leaders of American mosques hold extremist views and that Muslims do not cooperate with law enforcement have alarmed Muslim groups, some counterterrorism experts and even a few former allies in Irish-American causes.
Mr. King, son of a New York City police officer and grand-nephew of an I.R.A. member, offers no apologies for his past, which he has celebrated in novels that feature a Irish-American congressman with I.R.A. ties who bears a striking resemblance to the author.
Of comparisons between the terrorism of the I.R.A. and that of Al Qaeda and its affiliates, Mr. King said: “I understand why people who are misinformed might see a parallel. The fact is, the I.R.A. never attacked the United States. And my loyalty is to the United States.”
He said he does not regret his past pro-I.R.A. statements. The Irish group, he said, was “a legitimate force” battling British repression — analogous to the African National Congress in South Africa or the Zionist Irgun paramilitary in British-ruled Palestine. “It was a dirty war on both sides,” he said of I.R.A. resistance to British rule.
As for the hearings, he noted that counterterrorism officials from the Obama administration have often spoken, especially since a string of largely homegrown plots since 2009, of the threat from American Muslims who take on radical views. “Al Qaeda is recruiting from the Muslim community,” he said. “If they were recruiting from the Irish community, I’d say we should look at that.”
Mr. King’s witnesses at the hearing will feature a fellow House Republican, Frank Wolf of Virginia; Representative Keith Ellison, Democrat of Minnesota, who is Muslim; Dr. M. Zuhdi Jasser, a Muslim physician and activist who has been sharply critical of some fellow Muslims; and two family members of young men who embraced extremist violence. (The committee’s top Democrat, Representative Bennie G. Thompson of Mississippi, has invited Leroy Baca, the sheriff of Los Angeles County, who has praised Muslim assistance to law enforcement, and Representative John D. Dingell, Democrat of Michigan, who has many Muslim constituents.)
The furor about the hearing is less about the witness lineup, which does not seem especially incendiary, than about statements by Mr. King that appear to spread blame for terrorism to the entire population of American Muslims.
“This hearing is not focusing on the acts of a criminal fringe but is broad-brushing an entire community,” said Alejandro J. Beutel, policy analyst at the Muslim Public Affairs Council in Washington.
Mr. Beutel, who has compiled a database of terrorist incidents since 2001, said the problem of radicalization of young Muslims is serious, and his group has helped counter it with a number of measures, including a video featuring nine imams speaking against extremism that has become a Web hit. But he said broadly accusing Muslims of complicity in terrorism will hamstring the fight to prevent extremism, which depends on tips from citizens willing and unafraid to contact authorities.
Even Mr. King’s critics acknowledge a fundamental difference between the violence carried out by the I.R.A., which usually sought with varying success to minimize civilian casualties, and that of Al Qaeda, which has done the opposite. The I.R.A. was responsible for 1,826 of 3,528 deaths during the Northern Irish conflict between 1969 and 2001, including those of several hundred civilians, said the historian Malcolm Sutton
“King’s exactly right to say there’s a difference of approach between the I.R.A. and Al Qaeda,” said Tom Parker, a counterterrorism specialist at Amnesty International and a former British military intelligence officer. “But I personally consider both of them terrorist groups.”
Mr. Parker was at a birthday party for a friend in London in 1990 when the I.R.A. tossed a bomb onto the roof of the rented hall, a historic barracks. Many people, including Mr. Parker, were injured, but none died, by lucky chance of location and quick medical response, he said.
What troubles him, Mr. Parker said, is that Mr. King “understands the pull of ancestral ties. He took a great interest in a terrorist struggle overseas. He’s a guy who could bring real insight to this situation.” Instead, he said, “he is damaging cooperation from the greatest allies the U.S. has in counterterrorism.”
Some who have been close to Mr. King agree. Niall O’Dowd, an Irish-born New York publisher and writer who worked with him on the peace process in the 1990s, broke publicly with him Monday on his Web site, IrishCentral.com, describing Mr. King’s “strange journey from Irish radical to Muslim inquisitor.”
In Northern Ireland, Mr. O’Dowd said, they saw a Catholic community “demonized” by its Protestant and British critics and worked to bring it to the peace table. Seeing his old friend similarly “demonize” Muslims has shocked him, he said.
“I honestly feel Peter is wrong, and his own experience in Northern Ireland teaches him that,” Mr. O’Dowd said. “He’s a very honest, working-class Irish guy from Queens who’s had an amazing career. Now I see a man turning back on himself, and I don’t know why.”