George A. Smith expresses priesthood ban rationale.
George A. Smith, "The History of Mahomedanism," Journal of Discourses, 26 vols. (Liverpool: Orson Pratt, 1856), 3:29
The Lord conferred portions of the Priesthood upon certain races of men, and through promises made to their fathers they were entitled to the rights, and blessings, and privileges of that Priesthood. Other races, in consequence of their corruptions, their murders, their wickedness, or the wickedness of their fathers, had the Priesthood taken from them, and the curse that was upon them was decreed should descend upon their posterity after them, it was decreed that they should not bear rule.