The threat of offspring of interracial unions…

The offspring of interracial unions were threatening to whites primarily because they blurred the lines between what many of them understood to be a naturally superior white race and a naturally inferior black race. As long as there was a clear distinction between the two racial categories—in other words, as long as the two categories could be thought to be mutually exclusive—then the hierarchical racial regimes represented first by slavery, and later by legal segregation, could be more effectively defended. The existence of interracial children destabilized and threatened the understanding of racial groups as essentialized categories that existed prior to, and independent of, human norms and understandings. To put it differently, interracial children showed that racial categories, seemingly distinct and immutable, were instead highly malleable. Therefore, from a white supremacy perspective, it was important to try to deter the creation of interracial children as much as possible, and the ban on interracial marriage was a crucial means to attaining that goal.

Carlos A. Ball, “The Blurring of the Lines: Children and Bans on Interrracial Unions and Same-Sex Marriages,” Fordham Law Review, Volume 76, Number 6 (2008): 2733-2770.