Racial categories seemed inevitable because host sciences claimed empiricism.

Evidence

The peculiar hold on late-nineteenth-century liberal European culture of such relatively punitive ideas will seem mysterious unless it is remembered that the appeal of sciences like linguistics, anthropology, and biology was that they were empirical, and by no means speculative or idealistic. Renan’s Semitic, like Bopp’s Indo-European, was a constructed object, it is true, but it was considered logical and inevitable as a protoform, given the scientifically apprehendable and empirically analyzable data of specific Semitic languages. — Edward W. Said, Orientalism, 585

Categorization

• XREF: The prestige of empiricism legitimizing constructed categories is the same dynamic now at work in evolutionary-psychology and IQ-based racisms; connects to how ‘scientific’ framing launders prejudice.
• corroborated: 2 independent passages support this claim — Edward W. Said, Orientalism, 585