Segregated public schools in 20th century America were based upon the supposed legitimacy of "separate yet equal".
“I must say that black and white, as forms of speech, and as a means of judging mankind, should be eliminated from human society. HUMAN BEINGS ARE PRECISELY THE SAME whatever colour, race, creed or national origin they may be."-- Emperor Haile Selassie I (1963)
His Majesty was masterful in how he selected His words. “Precisely the same” is a very specific and powerful way to say that humans are not different in any core way from each other; and, not surprisingly, His Majesty’s pronouncement over a half century ago to this effect was scientifically prescient in that He spoke these words long before the human genome had been mapped and studied extensively on a comparative basis to confirm the scientific soundness of His Holy Perspective.
“Black supremacy” may not be a racist doctrine in the minds of those whose espouse it, but if we're using a terminology that 98% of the world HEARS as racist, then we know very well the visceral response that we are invoking by using it and cannot naively claim that we’re unaware that we are fomenting racial strife. The overwhelming majority of people who hear the term "Black supremacy" hear it as the same doctrine as white supremacy except with the colors reversed. They also understand “racial supremacy” to signify a notion of one race being superior to others (ref. "until the philosophy which holds one race superior and another inferior is finally and permanently discredited and abandoned....the dream of lasting peace and world citizenship and the rule of international morality will remain but a fleeting illusion, to be pursued but never attained"). Fanning the flames of racism is racism.
I have suggested that people who want to avoid provoking racial strife in this way might choose to substitute a use newer, clearer terminology for the misleading terminology. When I’ve suggested this specifically with respect to the clearly provocative terminology “Black supremacy” it has been strenuously rejected. Look how many terms have been changed in modern times to better communicate their true meanings and avoid creating unnecessary tensions, especially in the area of race relations. This just seems like a no brainer unless we derive some covet pleasure out of watching people writhe in the misunderstanding we're creating. It really comes down to the perception that we desire to communicate: angry and elitist or tolerant and inclusive.
If Haile Selassie felt so strongly about the toxic potential of describing humans as "black" and "white" that He called for these words to be eliminated in that context, then I'm sure He was correct. He tends to repeatedly demonstrate to us His Wisdom. Surely, there’s a way express the core values of a concept like “Black supremacy” without fomenting racial strife. If there isn’t then one must reflect very seriously on where this doctrine really stands on the spectrum of good and evil.
From the spiritual standpoint, any human can find JAH in their heart and life, and profoundly experience His Love. It's very difficult for me to fathom any Rasta who wants to alienate a fellow human being whose eyes are opened to RastafarI (but then just because it's difficult for me to fathom doesn't mean it doesn't occur).