If Anders Behring Breivik is insane, his "ideology" is secondary to his mental pathology. If he is sane in we should look at his ideology, methodology, and goals. Breivik considered the EU/EUSSR totalitarian in nature. He wrote a manifesto calling for revolution, not working within the legal systems of Europe. If the response to this terrorism is to suppress non-violent nationalists and anti-racist conservatives, then the winners will be the violent racists and revolutionaries. Opposition will be moved underground where it will fester and become violent and that is his goal. Any persecution of non-violent anti-Jihad activists or traditionalist conservatives will only help foster revolutionaries and terrorists.
The way to prevent a future violence is not to reward Breivik, but for democratic governments to work with political groups in rooting out violent people, while preserving the rights or opposition movements. There has been plenty of revolutionary violence in Europe from the left, but no one calls for ending the Social Democrats, Greens, and other non-violent movements despite splinters. The Right should be accorded the same respect to prevent more violence in the future.