I for one am not trying to claim there was never a religious component to The Troubles. The fact that the two sides lined up on sectarian lines was down to the complex political history of Ireland and the British, something of course that reflected the centuries old religious and political turmoil between the Catholics and Protestants. In that respect they are intrinsically linked and those divisions still exist in the 6 counties.
The point though is that the IRA did not target Protestants purely for their religious beliefs (ie. seeking to change them) - it was for their support for the union with the British. The violence escalated for political above religious reasons. If it had been possible to broker some peaceful solution before Bloody Monday (or if that had never happened) then The Troubles may never had occurred as the goals were political not religious.
I don't mean to diminish the sectarian divide - it still dominates aspects of life in NI as well as having parallels in Scottish culture as well - it's just that no Catholics were ever out to kill every Protestant or vice versa in NI - it was about doing what was needed to try and secure the political aims. The IRA did not have a religious wing, it had a political wing - Sinn Fein. Of course individuals and communities were targeted just for being Protestant or Catholic but ultimately for what they represented politically.
In terms of ISIS, yes they may have political objectives in terms of land grab but the overriding drive comes from theological ideology. You could give ISIS a whole bunch of land and vow never to talk to them again but they would still want you as an infidel to die.
This all comes from the divisive nature of simply following a religion. Most, if not all, religions teach that believers are better than non-believers. Most, if not all, incorporate rituals and behaviours that identify the believer as different - actions that if not followed lower your credibility within the faith.
Christianity has for the most part had these actions undermined to the point where they are an irrelevance. Even for believers it doesn't really matter if you don't take things as literally or fundamentally as once before. The same is not true of Islam.
I don't fully agree with Simon in terms of how far I think we should go in challenging Islam and Muslims in general as I think we might disagree on the danger posed by a so called moderate Muslim, however I do think it is time for all Muslims to examine their own beliefs and what the various rules and traditions they follow really says about their willingness to be inclusive and tolerant.
I find it very difficult to believe that the extremist mentalities will ever really diminish until the majority of Muslims truly are moderate and have dumped all these medieval concepts of morality and social hierarchy. Simply accepting an ideology that promotes division, even at a low level, puts you into conflict at some point with a society that is permissive and inclusive.
I would add finally that this is not an issue only with Islam. It's an issue for any type of fundamentalist belief and is no better illustrated than by Jehovah's Witnesses.