"Being a rational animal is (according to Aristotelians) the essence or substantial form of a human being; having black or white skin is not part of this essence"
Philospher Ed Feser showed that Black or White racism is anti-Thomistist and anti-Catholic:
Those features that are essential to a thing comprise what Aristotelians call its substantial form – the form that makes a thing the kind of substance or thing that it is, its essence. Being round is part of the substantial form or essence of a ball; being blue is not. Being a rational animal is (according to Aristotelians) the essence or substantial form of a human being; having black or white skin is not part of this essence; since someone can be a rational animal , and thus a human being, whatever his skin color. As with actualities, forms come in a kind of hierarchy. There is the substantial form or essence of a thing (e.g. being a rational animal in the case of human beings); there are various properties of a thing that are not part of its essence per se but which necessarily flow from its essence (e.g. having the capacity for humor, which follows from being a rational animal); and there are a thing’s “accidental” features, those which it may have or lack, gain or lose, without affecting its essence (e.g. being bald, in the case of a human being). [https://afteraristotle.net/2015/01/21/universals-in-fesers-the-last-superstitution-a-neo-aristotelian-alternative-to-realism-in-the-theory-of-universals/]