Al qaeda's ideology is quite simple. They reject modernity, they reject individualism, they reject modern commerce, and industry, and open societies. They want to end the influence of the western, liberal world on the arab/islamic world so that the latter can be returned to or preserved as a bastion of conservative and traditionalist culture and religion. Norwegians are as objectionable to their ideology as Americans, as they represent precisely those forces that they are fighting against (hedonism, personal liberty, etc.)

Aside from that, Norwegians have not shown as much respect or deference to Islam as al qaeda imagines they should. Norwegian newspapers reprinted the famously blasphemous "Mohammad cartoons", for example. We may not imagine that such a thing is important, we may imagine that free expression including blasphemy is indeed even a right that all people should have, and I think we should. But we shouldn't have any illusions that there are a lot of people who think otherwise. Who believe that blasphemy, heresy, and apostasy should be banned and punished to the most severe extent even up to death. It's curious to me that so many people could so easily misapprehend the motives and ideology of so prominent a movement as militant Islamism and so prominent an organization as al qaeda.