He wrote a book arguing the black people, as a race, are less intelligent than white people.
http://en.wikipedia.org/wiki/Ashkenazi_Jewish_intelligence
My own guess is that for some blacks, there has not been enough time for the Flynn Effect to occur for them to catch up with the general population. This is not due to any fault in them, but a result of no/substandard education for many generations. I imagine in a few generations any difference from the average will disappear. http://en.wikipedia.org/wiki/Flynn_effect
Would have been curious to get an opinion by somebody who read it recently.