|An alien in the Empire?|
What's wrong with this photo? Well, the Inquisitor is an alien, a Pau'an to be precise. However, the Empire as depicted in the Original Trilogy clearly had strains of xenophobia. Imperial ships were only staffed with human crews. White, male humans. Hearkening back to my posts on Images of Power, the Empire was clearly not a friendly place for aliens.
So, is an alien Inquisitor a continuity error? Of course, much will depend on how he is used in the TV series. However, there are both real-world and in-universe reasons to suggest that an alien might be able to rise through the ranks of a xenophobic empire.
Within the Star Wars Galaxy, we actually do see Emperor Palpatine/Darth Sidious interact quite frequently with aliens. Sidious' master, Darth Plagueis, was a Muun, and his apprentice, Darth Maul, was a Zabrak. In the novel Darth Plagueis, there is no hint that Palpatine begrudges either his master or his apprentice for their alien heritage.
More importantly, Palpatine apparently did not purge aliens from the Republic bureaucracy when he became Chancellor and later Emperor. In The Phantom Menace, then-Senator Palpatine points out that Vice Chancellor Mas Amedda, a Chagrian, is one of the more influential individuals in the Republic. However, far from removing him from power, Palpatine seems to take him on as a trusted advisor. In Attack of the Clones, Mas Amedda even appears cognizant of Palpatine's plans and helps manipulate Jar Jar Binks into proposing emergency measures. In Revenge of the Sith, Mas Amedda and another alien, Sly Moore (an Umbaran), are standing right by Palpatine's side when Palpatine announces the New Order. While we do not see either character in the Original Trilogy, we also do not see Coruscant and have no reason to believe that these political survivors were removed from power based on their species.
|The second most powerful man in the Empire?|
In the real world, autocratic regimes tend to have less diverse governments or exhibit systematic discrimination against minorities. However, except for regimes such as South Africa's apartheid based on racial grounds, even the most autocratic governments find themselves in a more ambiguous relationship with ethnic minorities. Governments might discriminate against ethnic minorities, but also must take care that doing so will push ethnic minorities to take up arms against the government. Frequently, governments will attempt to make symbolic displays of diversity. Indonesia's New Order regime set up cultural parks that allegedly showcased the country's diversity, even though in practice Javanese tended to hold the most political power. In Myanmar before 2011, the military was engaged in armed conflict against multiple ethnic insurgent groups, but still managed to promote an ethnic Mon to the rank of general (Gen. Myint Swe). There was a glass ceiling on promotions, but one that could occasionally be broken.
While we do tend to associate heterogeneity with tolerance and enlightenment, not all evil empires in speculative fiction are portrayed as homogenous. In J.R.R. Tolkien's The Lord of the Rings, Sauron's realm consists of orcs, trolls, humans, and other types of beings. By contrast, the humans, elven, and dwarfish kingdoms tend to be homogenous (Bree is a notable exception for its intermingling of men and Hobbits).
Overall, while we don't know what role the Inquisitor will play in Star Wars: Rebels or if his identity as an alien will play into his characterization. Nevertheless, I don't think the presence of one Pau'an in the ranks of the Empire necessarily detracts from the Empire's xenophobia. Rather, it could show some of the subtle tensions between autocratic government and ethnic diversity in the Galaxy.