Breivik had some fairly idiosyncratic beliefs which set him apart from many on the extreme right. There's simply no way of responding to every kook out there, especially if they hold views that are entirely fringe, and don't bother to try to make their case in a conventional manner.
IIRC, Breivik finished a book and released it just before his rampage; mass murder was therefore used as a publicity tool, rather than being the result of his views being ignored. He hadn't expressed his views in a conventional manner.
The mere fact that Breivik had a book (albeit a very incoherent, copied-and-pasted ramble of a book) makes him more akin to David Ray Griffin than the average YouTube link-spamming teenage Truther.
The USHMM shooter James von Brunn also had a book, the difference was that he'd self-published it some time before; and yet no one, not even in his milieu, really knew about it. His decision to assault the Holocaust Museum was apparently triggered by an entirely external cause, namely problems with social security and/or the tax authorities, which meant his pension was about to be cut. This particular kook had form, having previously been arrested for causing a disturbance in another federal building.
How do you respond to people like these? What possible attention could their beliefs have received that might have deterred them from their actions? From what I understand, Breivik was active online - one of millions who posts on the internet somewhere or other. So was von Brunn, albeit mainly in playpens for people of his own beliefs.
Both held beliefs they surely knew in their heart of hearts were fringe views - and thus, instead of opting for the normal publicity campaign route of promoting their beliefs and converting people to them through quasi-rational means, they opted for terrorism as a short-cut to achieving the publicity they wanted. At which point, the media and the public on the internet quickly worked out both were utter loons.
Two years on from von Brunn's PR stunt, he is seemingly mentioned nowhere on the far right that I can see, certainly not by Holocaust deniers, who ignored the incident from the get-go. Breivik seems to have provoked more conspiracy theories about patsies and false-flag attacks than he has won converts among the audience that might be most sympathetic to his views.
However, both of them articulated at least some views which are shared by wider audiences. Those views are still shut out. Who knows whether there will be further incidents. In Norway, I doubt it. In America, probably, but there have been so many nutters going postal in the US that it'd be hard to tell.
Obviously, the far right milieu is perhaps more likely to produce violence than, say, the black metal scene. But as you should know, living in Norway, the black metal scene has in the distant past indulged in murder. Should we worry about black metal being 'ignored'? Clearly it isn't ignored, black metal bands have been given Grammies in Scandinavia like they were Smarties, but the supposed Satanic 'message' which arguably resulted in several murders in Norway in the early 1990s and in Sweden in 1997 is certainly ignored.
