I understand that he followed the stab in the back myth, but it seems strange that he would believe that the Regime of Stalin was pro Jew when there was so much evidence to the contrary.
The figment of Nazi imagination that is Judeo-Bolshevism was part of the larger conspiracy theory that Jews controled world politics with an agenda against the "Aryan" race. Loaning concepts from such anti-semitic propaganda works such as the Protocols of the Elders of Zion, the idea of Jews controlling both Capitalism (as in Jewish Oligarchs and the Rothchilds controlling GB) as well as Communism was popular in Nazi imagination.
The idea is that Jews as well as Communism were both "international". The Jews as a race without a homeland and Communism as an ideology aiming to unite workers across borders. This has strong roots back in the 19th century when forming an ethnically homogenous nation state was part of the agenda of many rulers and Jews on the basis of earlier religious discrimination became sort of the odd man out.
The idea of Judeo-Bolshevism originated pretty much within Russia, even before WWI, and was particularly propagated during the Civil War against the Bolshevisks. Imported by German soldiers serving on the Eastern Front in Ukraine and POland, it found quick dissemination and was used against the Munich Soviet Republic, the November governement as well as against Bela Kun in Hungary.
Within this theoretical framework, it needs to be understood that due to the Nazi fighting with Communists before Hitler's ascent to power and due to their deeply ingrained anti-semitism and anti-communism, Stalin's anti-semitism or anti-semitic practices in the Soviet Union did not matter to the Nazis since they were convinced that it was all part of a Jewish plot to destroy the Aryans and Germany anyways and the Soviet Union was one of their tools.
As for one controversial discussion: There is some sort of historical basis. In the 19th century socialist and communist movements were in some places the only ones that didn't discriminate against Jews and agitated for their equality. Thus, many people who were discriminated against as Jewish (since the majority of them didn't practice Judaism and thus didn't perceive themselves as Jews) felt a certain gravitation towards these movements.
Sources:
Ulrich Herbeck: Das Feindbild vom „jüdischen Bolschewiken“. Zur Geschichte des russischen Antisemitismus vor und während der Russischen Revolution, Berlin 2009.
Lorna Waddington: Hitler's Crusade: Bolshevism and the Myth of the International Jewish Conspiracy, London 2007.
Arno J. Mayer: Der Krieg als Kreuzzug. Das Deutsche Reich, Hitlers Wehrmacht und die „Endlösung“,Hamburg 1989.
The CPSU was much more Jewish in the 1920s than in the 1930s, with names like Luxemburg, Trotsky(Bronstein), Zinoviev, Uritsky, and Sverdlov in the top ranks. During the Russian Civil War, the White armies made good use of antisemitic canards in their anti-Bolshevik propaganda. It still had many Jews in the 1930s, but in lower proportions, and Nazi propaganda is not exactly known for its watertight intellectual rigor.
Not to mention the fact that communism was grandfathered by Karl Marx, another Jew.