I can't remember where I heard it originally, but it suffers from the "This racism is a metaphor for racism" problem that a lot of sci-fi tends to get close to.

I can't remember where I heard it originally, but it suffers from the "This racism is a metaphor for racism" problem that a lot of sci-fi tends to get close to. The issue ends up becoming that by making the discriminated party/group a literal different species, or a robot, or an alien, you dilute the core moral argument about treating all humans the same in the real world. What should be about racism becomes closer to an animal rights argument in-universe about how to treat things that aren't human, but aren't completely inert, which is a much more nuanced argument. In short, metaphor is hard, especially when you're applying it to complex issues.