"When did the IRA kidnap and enslave thousands of Englishmen? When did the IRA send thousands of gunmen in order to take over Scotland? When did the IRA establish the death penalty for adultery? Where were all these IRA squads that were made up, not of Irishmen, but of Saudis, Egyptians and Moroccans?"
Well, they did go in for a bit of kidnap (enslavement being largely beyond their means - or ambitions, no doubt), and they did send armed Irishmen to England (and even Scotland, sometimes), Brendan Behan was one of them, sent to Young Offenders Institute for his part in the war-time Livepool bombing campaign; and I did no one republican who was reputed to have been given a beating for his homosexuality (though that was exceptional); and the IRA did get logistical help from, amongst others, Col. Gadaffi, ETA etc..
But Chris is right that their is a qualitative difference - I would say it was the context. In NI, there was a clear alternative of liberation v oppression. I am not sure that the Chechen 'independence' movement is not more like the Kosovan or the East Timorese - essentially an appeal for Western sponsorship rather than liberation.