Following the outbreak of war, he returned to Munich, performed pastoral work at the university, and established close contacts with Reform Catholic elements (i.e., elements that opposed political Catholicism, and politicians they regarded as too willing to make compromises with the Jews and "atheistic" socialists) in the city, especially the nationalistic Hofklerus at St. Kajetan.
In 1919, he first began publishing in the Münchener Beobachter, where he wrote relentlessly on the destructive influence of Jewish atheism and on the moral acceptability and necessity of ruthless persecution of Jews, even as far as pogroms, pursued in defense of the faith and institutions of the Catholic Church, and the example provided throughout the years by anti-Semitic leaders within the hierarchy.
By 1920, he was a leader of the secretive anti-republican Organisation Kanzler (Orka) and by 1923 he was the chief editor of the anti-Semitic daily Miesbacher Anzeiger and a leading journalistic figure within the broader volkish-anti-Semitic movement in Catholic Bavaria.
[5] As an increasingly prominent Nazi figure, he was the target of Social Democratic satire and portrayed as the anti-Semitic bishop of Miesbach.
[6] Multiple authors and eyewitnesses, such as Konrad Heiden[7] and Nazi "apostate" Otto Strasser, report that not only did Stempfle correct the galley proofs of Mein Kampf, but that he indeed copy-edited certain passages.