Assume for a second that they're right that a few points in assessed IQ make a significant difference in some agreed upon measure of success. If this is the case, you could test his hypothesis by actually controlling for age, race, and other factors, then tracking whether IQ is strongly associated with economic mobility after controlling for other factors. If he's going to make a statement about race and IQ, he should actually control for such factors, as the statement claims to be about IQ, making race merely a confounding variable. Even if they could show an association there, I doubt it's even possible to find strong evidence of a causal link, and even if you could find one, you should be careful with it, as jackasses with audiences would abuse it.
Regarding personal bias, I too have a personal bias. I think these guys are a pair of vile fuckwits, who like to use likely unprovable proxy arguments.