In The Republic where he exalted the Hellenes over the barbarian races and suggested a nation state run by Guardians who would oversee and control every facet of society from education to production including controlling domestic partnerships.

It was literally used as a blueprint to develop and justify fascism:

The cover of Hildebrandt's book left no room for doubt regarding the political sympathies of the author: it bore a swastika. In that very same year, Hildebrandt also published a translation of Plato's Republic in which he explicitly associated Plato and Hitler, presenting the latter as the philosopher guide of the dialogue. As a matter of fact, Hildebrandt's interpretation underlined many of the themes that were going to play a prominent role in subsequent Nazi propaganda and their appropriation of Plato, including an emphasis on Fuhrertum, racism, and, more specifically, eugenics.

• Towards Nazism: On the Invention of Plato’s Political Philosophy