It's not any of the inanity you hear from our leaders ("fascism", etc).
The real problem with Islam is, in fact, very simple. It's imams/maulvis/etc - the guys that run mosques, the Islamic versions of priests/ministers/rabbis/etc.
Specifically, it's that there is NO requirement of any kind to actually become an imam. Anyone can be an imam - just add the title to your name, and off you go.
Now, every other religion in the world has pretty stringent requirements. Wanna be a priest? Go get a couple of degrees at a seminary. Wanna be a rabbi? Hit the Yeshiva.
It may seem tiny. But this simple requirement has a huge effect. It (unsurprisingly) ensures a certain degree of quality, and weeds out the inept, the incompetent, the radical, and the bloodthirsty. At a deeper level, it forces people to engage with the real meaning of religion - not the nostrums taught by fundamentalists.
The result is that any idiot - and there are many of them - can set up a mosque; and, further, he can preach pretty much whatever he likes.
Combine this with the fact that the wealthiest Islamic countries - Saudi Arabia and Iran - are also the most radical; and you have a recipe to take an entire religion off the rails.
That's because these players are more than happy to provide copious funding for "imams" who meet their political agenda; since there are no requirements to actually be an imam, nearly every lunatic in the world who has such a political agenda can very easily be an imam.
The result is that moderate mosques and imams are being replaced at an alarming rate with the more and more extreme. The very fabric of the religion is being warped by a broken institutional structure married to an explosion in capital.
Now, that's not to say that this trend isn't affecting other religions as well. The rise of Christian fundamentalism in the States can be traced back directly to "ministers" who've done little more than study the Bible with their buddies.
No matter how earnestly they may have done so, this is no substitute for real learning at the hands of the more learned. It is how fundamentalism is born.
The point is that if you really want to help tackle Islamic extremists - the answer is simple, not complicated. It has nothing to with bombs.
It has to do with encouraging institutional change within the religion itself. It means ending the funding of religious "schools" which do little more than indoctrinate kids into murder. It means engaging with Islamic insitutions of learning, to discover which ones are real (and accrediting them), and which ones are just simulations (and discrediting them).
More than anything, it means helping Muslims find out whether their imams actually know anything - or whether they're just extremists off the street, with no knowledge behind them, who've been lucky enough to get enough funding to start a congregation.
Me, I think religion is mostly awful and stupid. I have a hard time understanding how people can believe in fairy tales of a glorious afterlives and miracles that seem to vanish whenever you need them most.
I've long thought that there was an existence proof God couldn't exist - if he did, why did he have to speak through people/prophets? Occam's razor dictates that if there is a God, he wouldn't worry about prophets; he'd just *poof* a Bible (etc) directly into existence.
But most of the world's 6 billion people - including mental giants like Bush and Ahmadinejad - think religion is desperately important. Fine. The answer isn't in violence - that will only beget more and more extreme violence. It's a sad nostrum today that every "terrorist" killed just creates 2 (5? 10?) more. This is a major error in strategy.
The solution is in religion itself - helping religion play the role it's supposed to play, by mending it's long broken institutional structure.
Of course, given the fact that "ministers" who are one step shy of con artists can fill up stadiums in the States, I hold out little hope for this to happen - though, very interestingly, accrediting imams is an explicit plank in the British governments response to the recent scare.
In fact, one could even argue that what's long been true in the 3rd world is finally happening in the 1st - that there is no political tool so sharp, cutting, or efficient as religion; and so Bush, Ahmadinejad, and their pals have every incentive to let the world rip itself apart in the name of religion (while their portfolios skyrocket).
NB - Wierdly enough, the Bishop of Rochester makes almost exactly the same argument today in the Telegraph - recommended.