Not denying the Nazis communism but calling them a petit bourgeois movement is a bit of an exaggeration. Sure they got a lot of their support was from the middle class but it was also from across German society. Ian Kernshaw even argues they were probably the only real national party( as in there support wasn’t restricted to one group/ geographical voting block) by the 1930s.
Note I also included the haute bourgeoisie in that statement. The Nazi party found its firm rooting in former soldiers, the former aristocracy, more well-off workers, bankers, and industrial conglomerates. Fascism arises as a reaction from the bourgeoisie, who are terrified of class consciousness and proletarian revolution, and the petite-bourgeoisie, who are terrified of becoming poor (or are already poor but either are not or cannot become radicalized; largely in part due to reaction from socialist uprisings---in Nazi Germany this manifested itself as fear from the Spartacist revolution, the Russian revolution, the Hungarian revolution, and the Red Biennium in Italy) and losing their jobs but not radicalized: it helps if they're unfamiliar with or at least not particularly well-versed in Marxism and/or politics as a whole. Fascism feeds on the fear of the petite bourgeoisie, whereas it
comes from the fear of the haute bourgeoisie; the petite-bourgeoisie and lumpenproletariat in pre-Nazi but post-Depression Germany were scared of losing their jobs, rocked by hyperinflation and economic mismanagement dating back to the Versailles treaty, hated the West due to the Americans pulling out economic aid and the French occupation of the Ruhr (as well as what would eventually become the Allies being most of the Entente; the United States, France, the United Kingdom, and eventually the Soviet Union as a successor of the Russian Empire), were anti-communist or at least feared Soviet expansion to the West, were filled with former soldiers and Freikorps members, and had convenient scapegoats; ethnic minorities (particularly Jews), political minorities (particularly communists), and foreign adversaries (particularly France and the USSR).
Fascism as a distinct ideology is a set of beliefs, funded and spread by the haute bourgeoisie. Think how Krupp, IG Farben, BMW, Ford, AEG, AP [Associated Press], Audi, Dresdner, and Hugo Boss among many other companies collaborated with the Nazis and supported their efforts against victims of genocide and the Nazi political system; Krupp produced Zyklon B and directly spread and benefit from slave labor, IG Farben produced Zyklon B and produced rubber using Auschwitz prisoners (killing roughly 23,000 of their 35,000 slaves), BMW benefitted from slave labor and used slaves in vehicle production, AEG used slaves, AP censored anti-Nazi sentiment and promoted pro-German articles in the States, Audi exploited slave labor (particularly at Leitmeritz; over 4,500 people were killed as a direct result of Audi using slave labor from that camp), Dresdner was the main stakeholder in Auschwitz and was the main financier and banking group for the SS in occupied Poland, and Hugo Boss was a fervent Nazi who made Nazi uniforms, and many other examples. I'd go all day listing them here.