I guess my take on this would be that ignoring or "getting past" passages like this is no less subjective than being upset by it. I don't really see how it's a question of objectivity.

Personally when I see things like this, I am taken aback, and often think how wrong it was that this line of thinking was ever so commonplace that it made it into a book with unrelated subject matter.

That said, I don't think I've ever just dropped a book after seeing similar. I don't think that makes me more objective. Perhaps less discerning? I've also finished books with brutal scenes of violence, and with simply terrible writing. I don't think finishing those makes me more objective either.