The Nazis hated Jews and Communists. Why? Because Communism was a Jewish idea, invented with a Non-Messanic Jew's best intents after he had suffered horrible Anti Semitism at the hands of the now-united German government and seen the Industrial Revolution be driven by Capitalism without common sense and compassion; and that is the only reason that the Nazis hated an ideology that had become equally as Far Leftist under Stalin as Nazism-- Nationalist German Socialist Workerism-- was.
Also, Far Leftists hate Far Leftists; and a Self-Hating Jew named Adolf Hitler who was as Leftist as-- or even more Leftist than-- Stalin hated competition. Just like control freaks, sociopaths, and others who manifest the worst of bad-enough human nature; Far Leftists hate competition.
On the other side are the Far Rightists like Ann Coulter, Jan Brewer, Michelle Malkin, and Laura Ingraham-- who, if you really probe them and watch them closely-- want nothing to do with anyone but their own-- and their own includes especially usually those of their own ethnic background and national and political ideology. For example, b'tzlacha ever being perfected-- especially a perfected Jew-- in Ann Coulter's eyes unless you're Dennis Prager, Mark Levin, or maybe even the late Meir Kahane. As for Jan Brewer, buena suerte con estando una persona aceptable unless you're a White, Anglo-Saxon, fully- or almost-fully gentile Protestant who was born to legal nless you're a White, Anglo-Saxon, fully- or almost-fully gentile Protestant immigrants or US-born citizens.
As for Anders Brevik, only in the passing of time will we find out whether he is actually Far Right or Far Left.