There was a lot of political posturing going on in German-speaking countries, but the line of the KPD was informed by the murders of Rosa Luxemburg and Karl Liebknecht by the SPD regime of Friedrich Ebert during the German revolution in 1918, not to mention the Bolshevik experience, and basically the entire experience of social-democratic treachery the world over at the time.

In Austria, it was even stranger. There, the ‘Austrian’ social-democrats had the same line as the Nazis on the Anschluss, that is to say, they also called for the unity of Germany and Austria into a single state. The Nazis hated the Austro-fascist regime of Engelbert Dollfuss so much that they murdered him in 1934, something which almost caused a split between them and Mussolini at the time. Later on, the Austro-fascists even re-legalized the ‘Austrian’ social-democratic party in an attempt to ward off the Nazi invasion in 1938, which went almost completely unopposed by the population. The ‘Austrian’ communists even went so far as to argue Austria really was (no joke!) a separate nation from Germany. The Bolshevik government itself did not oppose the idea of the Anschluss until after 1933.

There are even more crazy things that went on between communists, social democrats and Nazis in that place once called Prussia (yet another German-speaking country, this one the Allies didn’t see fit to allow to come back to life after the war), if you care to google it yourself. Also take note of how few SPD politicians were killed by the Nazis, and draw your own conclusions.