I don't think religion is a causal factor. I think it's simply a convenient justification and recruiting tool. Align yourself with a popular movement such as religion and it's easier to spread your ideology.
yes... this is again one of the better posts about this. whole argument is framed incorrectly by westerners. i don't know much about it myself, other than islam isn't going anywhere and in the dark ages, when Christians were killing each other in droves, ancient arab states and ottomans in the near east were kicking ass on every scientific front and their was a brain drain from west and central europe to places like the ottoman empire and the levant, just as germany and subsequently all of europe experienced a brain drain leading up to and during WWII that greatly benefited the U.S.
there are still globally plenty of killings done by xtians, many posters just don't know or hear about it or worse ignore it/trivialize/even rationalize it..and our domestic terrorist threat (which is many times larger than the foreign one--has a heavy xtian component and a strong correlation to whites and nobody is freaking out about that.. nor do we blame our bible and our religion for these attacks.)
The common themes that are at play in the current, specific arab-islamic terrorism have more to do with economic hardship, politicial instability, familial instability, and overall way of life/societal destruction. The reason we lump these guys together is because of their religion (of which we see there are too many sects, just like xtians, to say they are all motivated by any one thing), but their common language, literature, heritage, geography and race are the actual foundations of their society, religion is secondary and a convenient rallying cry and justification.
If you think about ourselves..common language, literature, heritage, geography, and race are the foundations of our culture and our motives have to do with economic advantages, oil, oversized military, fear, bigitroy and xenophobia, etc.--not our religion which itself has had many, many more sects than 400 year old Islam ever has.