I think James Watson's claim is that there is a difference, and that that difference is caused by genetics.
The quoted claim includes:
- inherently gloomy about the prospect of Africa
- people wanted to believe that everyone was born with equal intelligence
His claim appears to be contrary to current summaries on the matter, for which Wikipedia summarizes:
Genetics of race and intelligence ends with,
A 2005 literature review article by Sternberg, Grigorenko and Kidd stated that no gene has been shown to be linked to intelligence, "so attempts to provide a compelling genetic link of race to intelligence are not feasible at this time". Hunt (2010, p. 447) and Mackintosh (2011, p. 344) concurred, both scholars noting that while several environmental factors have been shown to influence the IQ gap, the evidence for a genetic influence has been circumstantial, and according to Mackintosh negligible. Mackintosh however suggests that it may never become possible to account satisfyingly for the relative contributions of genetic and environmental factors. The 2012 review by the Nisbett et al. (2012) concluded that "Almost no genetic polymorphisms have been discovered that are consistently associated with variation in IQ in the normal range". Hunt and several other researchers however maintain that genetic causes cannot be ruled out and that new evidence may yet show a genetic contribution to the gap. Hunt concurs with Rushton and Jensen who considered the 100% environmental hypothesis to be impossible. Nonetheless, Nisbett and colleagues (2012) consider the entire IQ gap to be explained by the environmental factors that have thus far been demonstrated to influence it, and Mackintosh does not find this view to be unreasonable.
These statements are more recent than the 2007 claim in the OP.
In summary they're not ruling out the possibility of new evidence in the future (for the theory that a difference in average IQ is genetic instead of environmental), however "several environmental factors have been shown to influence the IQ gap", and genetic factors haven't been isolated such that they'd reliably predict these differences.