The way Illyrians were segregated into Illyrian and non-Illyrian cities except for people who could pass echoes the Jim Crow era of US history, with black people being segregated and some of them trying to pass for white.
The refusal of service to those who were found to be Illyrian is like antisemitic attitudes in pre-war Nazi Germany, or the refusal of service to homosexuals. Most of what happened can be compared to any persecuted minority, racial or sexual.
That’s the beauty of a good metaphor. And the ugly universality of bigotry.