What happened last week in Oslo is shocking beyond belief. This should go without saying. The way media and politicians reacted on-the-hoof and made rash assumptions about the identity of the perpetrators is equally as shocking and potentially dangerous in its implications. A mosque in Luton was attacked by the English Defence League on the pre-text of 'retaliation' for the Oslo attacks; ironic, considering the main perpetrator was a political fanboy of theirs. Several media outlet's and certain MP's would do well to reflect on the saying that 'careless talk costs lives'.
However, now the identity of the main attacker is known we can start the process of ensuring that we act to prevent or at the very least mitigate the chances of a similar occurrence. Central to this is an understanding of motive and cause of the horrific events that unfolded yesterday. This is a complicated question and there is no one simple one-size-fits-all answer - politics and political convictions are usually somewhere in the mix, as is the belief that the actions in and of themselves are justified (so, there might be a recognition that these actions are wrong, but they are still ultimately justified in the perpetrators eyes) by a recourse to a perceived 'greater good'. It's therefore not surprising that religion, as well as politics, is a body of ideas which can easily provide the justification sought because by it's very nature it is about conceptualising and codifying an authority or power that is greater than us.
Furthermore, it is, of course, not unheard of for terrorist groups to use religious subtexts to justify their actions or to have a background of cultural investment in religious belief. A lot of Al-Qaeda's actions are laced with religious rhetoric and self-righteous glorification of their struggle in religious terms and from the Christian side, Timothy McVeigh, the Oklahoma City bomber was a devout Christian. It is possible the Oslo attacker is going to turn out to be the same. However, in each case, the programme and stated goals are essentially political in nature and this shows how toxic the relationship between religion and politics can be; and part of the answer to the above question is the mix between religion and politics partially is. We would not however, ask 'is politics to blame' in quite the same way and that shows the dangerous of a simplified blaming of religion.
Religious ideas are generally, by their very nature, diffuse and there is a strong element of being able to make of them what you will. So, it is utterly true that far from Islam being the only religion which contains extremist elements it can and is true of all religions, including Christianity, and this is especially true of monotheistic religious thought-forms because they insist of the divine supremacy and absolute truth vested in one singular god. Monotheism thus lends itself to supremacist ideas and ideals by very dint insisting it is the 'singular divine truth' (by implication anything else is unholy and untrue etc, etc). Polytehsic religions are naturally likely to be more tolerant of diversity both culturally and of different belife patterns because they are conceived in that way. This is no doubt why monotheistic churches have been responsible for the instigation of what is effectively state terror on the practitioners of other religions as well as inter-faith wars (think the Christian Church and it's barbaric campaign of terror directed against paganism and pagans or the numerous inter-faith wars such as the Crusades, etc).
However, ultimately, it does come down to if you can blame a body of ideas for the interpretation people have of them and the actions they take consequentially. Ideas are not sentient entities and people are so, I rather think you can't, not entirely in any case. You can certainly see the genesis of how religious ideas can become the pretext for barbaric actions in a way I have outlined above. However, it is worth noting, that just as equally they can be the pretext for acts of great compassion and generosity; great good in other words and to say they are entirely to blame would be to fail to realise that contradiction even exists. It's a contradiction that has its explanation in the vaugeness of religious texts and a complicated web of factors external to religious ideas and how they both interact with the outside environment and are shaped by people within that environment; there is a wider story to be told and that does involve other issues including both extreme social and political alienation, political factors such as policy (ie, wars etc), and the development of terrorists as individual human beings ie, their personal psychology. It's only when these factors are into consideration that you being to form a complete picture of a complicated issue.
Some people will say even considering this issue is wrong - that these people are simply 'evil' - but even if that were the case then the question has to be asked why are they so. A retreat into metaphysics isn't helpful if we are to prevent further atrocities - a key component of which is understanding the causes of what occurred in the first place. If we can get to grips with the 'why' and the 'wherefore' then prevention becomes much easier - it's tempting to reach for knee-jerk answers but, returning to the top, those are usually the wrong ones which can be as damaging to innocents as the actual attacks themselves.