As with any kind of thinking, it can be used or misused.
One of the authors of the book died before it hit the bookstores. I caught the other author on CSpan before I bought the book. He talked about the learning that children are exposed to in their homes before they reach school age, while their brains undergo their maximum lifetime growth.
Cultures can either provide or deprive children of the kind of stimulus that can impact their lives for better or worse.
It's been years since I read the book, but I don't think it went into the genetics of race, which would be a pointless discussion. Arguing the superiority of one kind of culture over another, OTOH, is something that could improve the lives of some if it wasn't against the rules of PC to do so.
My point would be that the findings of science are not affected by their possible misuse, any more than the makers of guns are responsible for their misuse.
As for Darwin and racism, any honest person who reads about him would find that he argued against slavery at times and places where it caused him considerable personal inconvenience.
He probably believed that isolated groups of people could differ, as a group, in many kinds of abilities. In the abstract, I’m not sure there is a way to argue against that.