To assume that all members of the Workers' Youth League (AUF) are "typical Norwegians" (not a direct quote) is a bit misleading. Many of the victims were people of colour (children of immigrants and refugees). Or they were white young people who believe that Norway should welcome immigrants and embrace cultural diversity.
The AUF is the official youth organisation of the Norwegian Labour Party. Many AUF leaders have gone on to become members of the national parliament and government ministers - including Norway's current Prime Minister Jens Stoltenberg (who has attended every AUF summer camp since he was 15 years old - either as a participant or as a guest).
Breivik deliberately targeted this camp to inflict physical and psychological damage on the Labour Party, to weaken the next generation of political leaders (on the left) and make it more difficult for the AUF to recruit new members in the future.
Based on what we know about Breivik's world view (from his video and book), there is nothing surprising or puzzling about his choice of targets. Let's not be naive.
Would we be surprised if a right wing extremist in the US decided to target the national convention of the Young Democrats of America? (I hope the YDA has armed police protection)
http://en.wikipedia.org/wiki/Workers%27_Youth_League_%28Norway%29http://en.wikipedia.org/wiki/Norwegian_Labour_Partyhttp://en.wikipedia.org/wiki/Jens_Stoltenberg