The picture that's emerging is of an ordinary right-wing man stoked into anger by theories about "Cultural Marxism" that originated on the anti-Semitic far right but have in recent years been spreading into more mainstream venues, promoted by the likes of Andrew Breitbart, among others.
You can read for yourself Breivik's postings to the Norwegian site Document.No (application/pdf - 211.61 KB) (translated here), which should give you a clear enough picture.
Chip Berlet, who specializes in analyzing right-wing extremism, has been going through them, and here are his initial thoughts:
Based on online posts apparently by Anders Behring Breivik circulated in Norway, the alleged terrorist opposed multiculturalism and Muslim immigrants in Norway. Breivik championed opposition to "Cultural Marxism," a right-wing antisemitic concept developed primarily by William Lind of the US-based Free Congress Foundation, but also the Lyndon LaRouche network.
... The idea is that a small group of Marxist Jews who formed the Frankfurt School set out to destroy Western Culture through a conspiracy to promote multiculturalism and collectivist economic theories. A key "Cultural Marxist" guru William Lind spoke at a Holocaust Denial conference, and worked at Free Congress Fdn. which sponsored a former Nazi collaborator, the late Laszlo Pasztor. See Bill Berkowitz article on Cultural Marxism for Intelligence Report at SPLC website .
Bill Berkowitz reported on "Cultural Marxism" as a far-right organizing concept for the SPLC back in the summer of 2003:
At the core of the far right's concept of cultural Marxism are the Jews. Lind made this plain in June 2002, when he gave a speech on the subject to a Washington Holocaust denial conference hosted by the anti-Semitic journal, Barnes Review.
Although he told his audience that his Free Congress Foundation was "not among those who question whether the Holocaust occurred," he went on to lay out just who the cultural conspirators were: "These guys," he explained, "were all Jewish."
Like Jews in general, the Frankfurt School makes a convenient antagonist — one that is basically seen as antithetical to all things American. The school, says social psychology professor Richard Lichtman of the Berkeley-based Wright Institute, is "a convenient target that very few people really know anything about.
"By grounding their critique in Marxism and using the Frankfurt School, [cultural conservatives] make it seem like it's quite foreign to anything American. It takes on a mysterious cast and translates as an incomprehensible, anti-American, foreign movement that is only interested in undermining the U.S.," he said. "The idea being transmitted is that we are being infected from the outside."
Not everyone who uses the cultural Marxism construct sees Jews in general at the center of the plot. But a 1998 book by California State University-Long Beach evolutionary biologist Kevin MacDonald — one of just two witnesses to testify on behalf of Holocaust denier David Irving in a famous 2000 libel trial — makes plain that Jews in general are implicated in what is seen as an attack on the West.
In The Culture of Critique: An Evolutionary Analysis of Jewish Involvement in Twentieth-Century Intellectual and Social Movements, MacDonald says that while all Jews are not guilty, the movements he attacks are indeed "Jewishly motivated."
In a chapter devoted to the Frankfurt School, MacDonald suggests that Jews criticize non-Jews' desire to form "cohesive, nationalistic, corporate gentile groups based on conformity to group norms" — with Frankfurt School principals painting this desire as a psychopathology — while they hypocritically pursue cohesiveness in their own group.
As Berlet explains:
The trope of Cultural Marxism combines this view of political economy with a narrow view of Christian superiority and an ethnocentric White Nationalism. In both sectors--Christian superiority and ethnocentric White Nationalism--there is a great fear of Muslim immigration. .
Among right-wing Christians who fear Muslims there are some that see Islam as the false religion of the Antichrist in the End Times in their idiosyncratic reading of Biblical prophecy. This apocalyptic view is widespread in some areas. For example a poll found that 15% of Republicans in New Jersey though President Barack Obama might be the "Antichrist" who is Satan's chief henchman in the End Times. Another 14% were convinced Obama was the Antichrist. Whether it is based on religious or secular themes, the idea of a vast longstanding conspiracy of Cultural Marxists to destroy Western Culture creates apocalyptic aggression, in which believers in the conspiracy theory decide to act first against the named enemies.
The concept has been mainstreamed in recent years, promoted -- in a form stripped of its anti-Semitic elements -- by a number of supposedly mainstream conservatives. We knew we had heard the phrase bandied about the past couple of years on Fox News, and went looking in Google to find out where we had heard it.
Originally we thought the chief culprit would be Glenn Beck, who has indeed made a fetish out of Marxism on his show. But the chief promoter of the concept of "Cultural Marxism" on Fox News was none other than Andrew Breitbart:
Breitbart has made a number of attacks on "Cultural Marxism" as a liberal phenomenon -- such as his insistence that "political correctness is Cultural Marxism". Indeed, Breitbart has made something of a fetish about using the phrase. Likewise he has made something of a fetish out of "Frankfurt School" theories.
And as you can see from the above video, he got a nice national platform to promote the concept back in 2009 on Sean Hannity's Fox News show -- twice. This is a classic form of what acting as a "media transmitter," repackaging ideas that originated on the racist/anti-Semitic Far Right and injecting them into the mainstream.
This is not to suggest in any way, of course, that Breitbart is connected directly to the Norway terrorist attacks nor even that he is by any means responsible for them. It's clear, however, from Friday's events that the ideology he promotes radicalizes people and indeed ultimately invites and inspires extremist violence. Considering his legion of right-wing fanboys in America, that's cause for concern.