A person that believes classes are real (ie, a realist, like a cladist or a particle physicist) is also a racist. The difference between him and a person that understands classes are merely abstractions in our minds (ie, a nominalist, like a traditional scientist) is that the realist believes we can find out what a thing is, whereas the nominalist understands it is we that decide what a thing is. Only a realist can thus come up with the racist idea to measure sculls to “identify” which race a person “belongs to”. A nominalist instead understands that we can cut reality in many different ways, all of which are fundamentally paradoxically contradictory, thus resulting in a class containing “the rest”.
The only way there is to avoid the paradoxical contradiction of classification is by an orthogonal system of classification, like the Linnean systematics of the biodiversity. Suxh system avoids the paradox by partitioning classes into two levels, thereby avoiding the middle between them, because the paradox resides in this middle (which is also the meeting point of them, ie, the interface between realism and nominalism).
The problem with the nominalist avoidance of the paradox is that if a nominalist (like Linné) uses it to classify something, then this classification appears to support a realist’s (like Willi Hennig’s, “the father of cladistics”) belief that classes are real by providing a consistent classification. The nominalist solution thus fuels the realist approach. It means that the realist can use the nominalist solution as an elevator from nominalism down to realism, as Willi Hennig did, an operation commonly called “triangulation”, catalyzed by some theory of how classes have originated (in this example, Charles Darwin), with a slight change of the system (in this example from polytomies in the Linnean system to strict dichotomy in realism (ie, Willi Hennig’s system). The realist thus utilizes the only consistent solution to avoid the paradox of classification as a support for his notion that there is no such paradox, by claiming that the solution shows that there is no such paradox (at the same time as adjusting it slightly to fit a realist theory of how classes have originated).
The problem with this triangulation is that it only leads us back from an orthogonal to a “flat” classification (thus containing some class that collects “the rest”. The problem with cladistics is that this class is hidden somewhere in every “tree of life”, and since cladists can’t understand that it is, the problem is in practice invisible to them. Instead, they are surprised that no tree can incorporate properties (which they call character states) consistently. Cladists are thus surprised of the consequence of their own inconsistency). The triangulation thus just turns the steak up-side-down from a consistent nominalist to an inconsistent realist approach.
This reasoning is a merry-go-round between consistent nominalism and inconsistent realism. Every nominalist solution of the paradox of classification is by realists taken as a support for their belief that there is no such paradox. In this merry-go-round, we can at least conclude that realists are racists, whereas nominalists are humanists (apart from that realists are inconsistent, whereas nominalists are consistent).