...again--main point is the Africans/blacks were so far behind whites BEFORE the exploitation/etc that it is hard to argue that the exploitation/slavery/oppression caused the problems with the blacks
Nonsense. Technological advancement does not make people better... we see that here every day when awful racists figure out how to use computers.
...is it possible that slavery/oppression/etc caused American black culture/education/etc to not advance? sure and probably did---but to what effect?? --
..what effect did the black culture/etc [ or lack of]
Uh, yeah, guy, 400 years of social and racial oppression will stunt your advancement... I'm glad you figured that out.
I don't think you are doing yourself any favors here, as you seem to conflate racism (a state of mind), institutional racism (organizational structures and aims reflecting the prevalent societal racism), and white privilege (a societal organization bequeathing benefits on the favored racial group). They may well be mutually reinforcing, and the end result sure is "to keep the other races in a subordinate position", but the same they sure are not.
Nice try, guy... but the fact is you can't really be racist without the institutional structure to back it up.