Stefan says white people have a higher IQ and they should not mix with other races. If he really thinks it, he shouldn't have a problem with being called a racist, because that's exactly what the definition is: thinking that your race is superior. Of course he says that he doesn't think whites are superior, they just have a higher IQ, blacks are better at sports, which really is a lame excuse. It's like saying we are not superior to gorilla's even though they are miles away intelligence wise, they are are really physically strong. It's just a way to say racist stuff and not feel racist by self-rationalization.
Anyway, like Sam Harris says, I have no time to research if there is scientific view in it so I reject it as racist, as most people would. I don't see anything wrong with that. Most philosophers are really liberal but Stefan is a basically right-wing nut in a lot of his views, supporting Donald Trump and conservatives in general.