The highest rate of Neanderthal admixture is in East Asians, but there is also a non-trivial rate (2-6%) in most Europeans. The admixture in sub-Saharan Africans is much lower, which creates a risk of any discussion of positive Neanderthal traits pulling in much broader baggage relating to race & genetics.

I think this is what the poster was talking about: race issues - that is, how (white) Europeans tend to have more Neanderthal DNA compared to, (black) sub-Saharan Africans. So if you show that some neanderthal gene provides some nominal increase in IQ, you'll have lots of people jumping on it as proof that whites are superior to blacks.

Of course, east asians and specifically melanesians have probably the most neanderthal DNA, maybe twice the amount of the average European, and I would love to hear a white supremacist argue for the genetic supremacy of Melanesians.