I don't completely disagree with you - the kind of schools Williams writes about (especially in previous columns) would create an entirely new black intelligencia, and do so much more for their people than is currently being done (black families were more stable prior to the welfare state, etc.). However, assuming races are the same across the board (on average) leads to expectations of similar results, across the board. This is one liberal excuse for affirmative action and all the other goodies - because 'leveling the playing field' still hasn't achieved similar results. The fact is, they never will.
I would love to be wrong on this (hopefully I am, but I don't see any evidence so far based on observation and history), but it does seem that average IQ correlates directly with economic status. It's not meant to be a slam at all, and it's certainly not meant to be hateful.