I just listened to the Lower Decks episode on The Omega Glory. The discussion was stimulating, as always. What I find most fascinating is the strange conflation of racial categories and systems of political organization.
Were I to trace the history of this style of racism, I'd be tempted to go straight to Tacitus. In using an alien group to critique his contemporaries (a very Trekian move), Tacitus gave birth to a very influential paradigm. Here's how Barzun puts it, in his book about race:
Tacitus wrote as traveler, historian, and moralist, but especially as an embittered foe of the Imperial tyranny. Hence his eulogy of the Germanic race is systematic and politically pointed. According to him, the Germans are an indigenous race; they are virtuous, individualistic, freedom-loving, and jealous of their racial purity; physically they are tall and blond, brave and tough, they live frugally, and are adventurous rather than toilsom. "What is very remarkable in such prodigious numbers, a family likeness obtains throughout the nation."
Some later Europeans drew on Tacitus when critiquing their own political institutions by locating contrary political inclinations in an outside group--the Germanic race:
Tacitus and his tract had already been used in France to meet a similar situation in the seventeenth and eighteenth centuries. Leaning on the Germania for a description of the special gifts and institutions of the Frankish or Germanic race, the Count Henri de Boulainvilliers (1658-1722) evolved the still lively notion that all political freedom comes from the Germanic strain. Hence, he argued, Louis XIV's absolute monarchy, based on the Roman idea of the imperium, was a government fit only for slaves. Boulainvilliers wanted the nobles of his day to revolt against slavish institutions and restore the aristocratic freedom of the German forest.
These images depict the Germans as proud upholders of freedom, but that wasn't the only way they were cast. At the onset of WWI, the Germans were routinely called Huns by their rivals, and their military triumphs likened to those of a Mongolian horde rolling across Europe. There's an historical irony here given the origin of the Hun moniker in a speech given by Kaiser Wilhelm where he bids his soldiers to be like ferocious Huns in guarding Europe and Russia from the "inroads of the Great Yellow Race". Fast forward a few years, and both Germans and Russians become purveyors of Eastern tyranny in Yellow Peril tinged propaganda.
As an aside:
There's a long history of linking Eastern peoples to imperialism from Herodotus onwards, but it need not be a racial thing. For example, Jiang Shigong, drawing on Montesquieu, affirms a connection between China and Empire, through material factors like geography.
Montesquieu was [however] a social theorist, and thus ultimately had to respect social reality. He noted that the great empires of the East were connected with an expansive geography. Because of this, he especially emphasized the inherent connection between geography, nature, and politics. In this sense, the basis for the legitimacy of empires/autocracies was rooted in geography.