They're terrorists. You might as well ask what beef Al Qaeda has with the US. Does it matter? If they have a 'legitimate' beef does that make it ok to bomb people? The IRA have always been on the same level as Al Qaeda. They're all murderous bastards who need to be destroyed. It should surprise no one that they are working on the same side.
I dare you to say that in South Boston on March 17th.
The comparison of the IRA to alquaeda is correct. Both groups are nothing more than people whose favorite thing to do is cause pain, suffering and death to others. They just use different excuses—“Irish sovereignty” vs “Islamic jihad.”