There's a difference between edgy social media comments from early adolescence -- which shouldn't be used to "cancel" anyone -- and passages from a book that this guy wrote and published when he was an adult (especially since he still hasn't retracted or apologized for anything that I'm aware of).
You make a good point about hiring, though. They could probably read reviews of his book, but I don't know whether the reviews would mention its sexist elements -- probably depends on when it was written.