it's the other side of the coin of advocating for interacial relationships to "improve the race," (mejorar la raza) which you see a lot in Latin America with the whole idea of blanqueamiento (whitening). It has analogues in the US in the form of colourism, but there are people that take that and run into full blown "race science" like "divesters" (black women "divesting" from black men) and SYSBM ("Save Yourself Black Man" [from black women]) types. It's pretty sad, especially when you see these people use this kind of race science to explain everything from black poverty to the failure of Reconstruction.

edit: admittedly those people are very online and super fringe, unlike the reactionary types of black nationalists, but it is interesting to note.