Even stipulating the imprecise language here, he couldn't "establish that his claims were true", because he did not work in these fields. This is a pop science argument where any "scientist" can just "do science" to answer deep or controversial questions, but obviously that't not how science actually works. His racist comments pertained to several highly specialized fields of study, none of which he worked in. You might as well have asked Neil DeGrasse Tyson.