As early as 1897, the country doctor gave antisemitic speeches at Franconian farmers' meetings. Before moving to Munich in 1913, he ran the Bad Burgbernheim spa and published on medical topics and areas bordering on psychology. One of his six sons was taken POW in France in 1914 and two others died in the war.
Dingfelder organized the care of POWs for the Bavarian Red Cross. From 1916, he wrote under the pseudonym Germanus Agricola. In September 1919, he became the regional chairman of the German War Graves Association. At the same time, he started the article series “Geldwahn und Rettung (Money mania and rescue)” in the Münchner Beobachter newspaper. Die Rettung des Mittelstandes (The rescue of the middle class) was published by Dietrich Eckart's Hoheneichen-Verlag. Dingfelder saw the solution to the plight of the middle class in a romanticized medieval community of production and consumption.
At the beginning of 1920, the German Workers' Party (DAP) took advantage of Dingfelder's high profile by announcing him as the only speaker on the advertising posters for a meeting on February 24, 1920. This first mass meeting of the DAP, attended by 2,000 people in the banquet hall of the Hofbräuhaus in Munich, gave Hitler the opportunity to present the 25-point program of the party, which was now called the NSDAP (Nazi Party). Since then, this date has been regarded as the founding day of the Nazi Party.
Dingfelder then worked for several years with Alfred Rosenberg as a journalist. In 1924, Dingfelder published the Großdeutsche Zeitung newspaper, a replacement for the banned Nazi newspaper the Völkischer Beobachter. In his 1930 publication Arzt und Priester (Doctor and Priest), Sigmund Freud was called “Salomon Freud”: the “Teufel als Affe Gottes” (Devil as God's Monkey). During the Second World War, he gave lectures on “rational fruit growing” and devoted himself to questions of “healthy public nutrition”. State Premier Siebert awarded him the “Ehrenzeichen für Volkspflege” (Decoration of Honor for Public Welfare) in 1940.