Comparisons between Islamic State and the IRA make it harder for republicans to sanitise the past and rewrite history, a DUP MP has said.
David Simpson was speaking after an American cardinal sparked controversy when he said Islamic State was a distortion of "genuine" Islam in the same way the Provisional IRA was a "perversion" of Catholicism.
New York-based Timothy Dolan told CNN: "The IRA claimed to be Catholic. They were baptised. They had a Catholic identity."
But, he continued, "what they were doing was a perversion of everything the Church stood for".
David Simpson, who represents Upper Bann, said "terrorism of 2015 is the same as terrorism of 1975".
"Condemnation of the barbarism perpetrated by the so-called Islamic State has rightly been universal," he continued.
"However, some people in Northern Ireland are uncomfortable when a light is shone on their very similar actions during the Troubles. They seek to justify their brutal crimes by saying it was for an honourable cause. This is complete folly. Terrorism of any hue was never justified.
"Islamic State has forcibly wiped out the Christian population in many cities within the Middle East. The only difference between that and the IRA's actions in isolated rural communities along the border is one of scale."
He added: "Many of those who were involved in terrorism in Northern Ireland are deeply uncomfortable with parallels being drawn. Such comparisons make it more difficult for them to rewrite the past and cleanse their conscience."
Relatives of IRA victims last night backed the cardinal's comments. Alan McBride, whose wife was killed in the 1993 Shankill bombing, said: "We can be thankful the likes of the IRA and others did not descend to the level of depravity we have seen from Isis.
"But there is no difference. Violence can never be the answer and the IRA, as with Isis today, were engaged in pure terrorism."
Ann Travers - the sister of Mary who was murdered by the IRA in 1984 - added: "The only difference is that we have social media which can show everyone the true horrors and instil fear.
"There is no difference to putting a firebomb in a hotel to setting someone on fire in a cage."
But former Sinn Fein spokesman and republican prisoner Danny Morrison yesterday strongly rejected the comparison as "ignorant" and "absolutely wrong".
Mr Morrison said: "There are massive differences, ideological and in terms of the IRA having been an indigenous organisation with clear aims, a historic organisation, an organisation which, yes, used force in conflict."
A Sinn Fein spokesman criticised the cardinal's remarks.
"The comments by Cardinal Timothy Dolan are misinformed and unhelpful. The republican struggle has always been political, not religious. We value the ongoing support for the peace and political process from Irish-America."
Mr Dolan is the spiritual leader of New York's 2.8 million Catholics. He said Islamic State "do not represent genuine Islamic thought" but is "a particularly perverted form of Islam."
"The analogy [to the IRA] is somewhat accurate," said Mr Dolan. "These are not pure, these are not real Muslims. Now what we need and what Pope Francis has led the world in saying, is we need the temperate, moderate, genuine forces of Islam to rise up and say this - they do not represent us. Now, that's beginning to happen. God can bring good out of evil."
Mr Dolan said Isis was currently carrying out a "systematic, well-choreographed, very well-focused attempt to eradicate the ancient Christian population in the Mid East".