You're kidding, right? What do you think "antiracists" are talking about when they are talking about whiteness?
A constructed identity, originally created by the European aristocratic class to justify differential treatment of different worker classes. Popularized as a claimed quasi-ethnic identity by later generations of Eurasian colonist descendants as a way to differentiate themselves from parent European racial/national identities without losing a sense of "consciousness of kind" associating them with their learned conceptions of civilization, pan-Christian identity, and racial superiority. This allowed them to continue the colonization of the American and African continents, as it separated them gocnitivrely and practically from the peoples whose lands they were appropriating, and justified continuing to deny rights to the slaves they were employing to work their fields and mines. Then most of the colonies rebelled or seceded from their ruling states altogether, and things got very complicated indeed.
Whiteness ultimately became a complex cultural category standing in for the owning classes, vaguely but persistently associated with mythical concepts such as divine providence and selection of certain peoples over others, an eternal European identity, technological supremacy, and superior social models. To be granted or denied "white" status by the elite class was the ultimate political tool, as it put a citizen of one of these revolutionary states in a wholly different legal situation, and associated them with a kind of imagined inherent status. After the 19th century, the idea of whiteness evolved a folk sociobiological component as well, supposedly standing in as a marker for inherited biological capacity for the lifeways associated with European conceptions of civilized, educated, and later, "cultured" life. However, its primary power has always been in the carrot-and-stick manipulation of the working classes by ether granting them whiteness and thus vaguely associating them with upward progress or denying it to condemn subjugated groups to hopeless drudgery. After the civil rights movements that swept the world after the second world war, whiteness evolved again out of a necessity to disassociate it from the now-disrespected fascist political philsophy of the losing sides of that war, becoming cloaked in implication and dogwhistled phrases rather than formal legal protections, though still semantically associated with European imaginaries of tradition, education, biological vigor, and fundamental capacity for success. It should go without saying that, having been cycnically created, these racial categories are intrinsically
dishonest, and misrepresent the universal human capacity for wisdom, productivity, and other values. However, on the political plain, the idea of whiteness has outlived all of its original moorings, and its associated semantic categories have proven to be a rich bed of keyed values that modern neo-fascististic movements across a broad swath of currenty or formerly European colonial polities are using to create new hotbeds of white nationalist rhetoric and political violence, now associated less with formal political endorsement than populism and the exploitation of general uneasiness with decaying class structures and industrial transformations in the wake of mass globalization and digital commerce.
If you're talking to anyone familiar with critical race theory, "whiteness" is considered the cognitive key that codes for this entire complex history and present, as filtered through the everyday experiences and perpetually incomplete knowledge of particular communities. Ultimately, whiteness can only be sustained as a concept by continuing to promote fundamental inequalities, so the anti-race movement has risen to more or less expunge it from our collective vocabulary and worldview, continuing in the realm of the mind and culture what was once fought within the constructs of legality and authority by the Civil Rights Movement and its cousins. The post-"race" world will hopefully be post-racial, but not by any means post-cultural. If anything, the "white" colonists of the past were just as much robbed of their family and cultural roots as anyone else, albeit not as violently as those from whom these were violently appropriated, and many whites suffer a strong sense of existential groundlessness, lacking any specific knowledge of where they have come from and envious of those whose lines of cultural transmission were never broken despite deprivations. The world after "race" will naturally be culturally richer, celebrating communities, heritages, and societies rather than inconsistently applied categories of skin pigmentation.
