C S Lewis wrote based on the period he lived in. At that time, in WWI, only men were soldiers though women could go to the battlefield as nurses. The Arabs still had slaves while there were no slaves at that time in the UK.

This is similar to other books from the same era. Gone with the Wind has become very controversial, for example. It has nothing to do with Christianity. Neither do Huck Finn and A Connecticut Yankee in King Arthur's Court by Mark Twain or Somerset Maugham's Of Human Bondage.

Anna Karenina might be considered misogynistic, except it accurately portrays life in that time and place. Pride and Prejudice reveals misogyny and class prejudice in British society - does that make it a bad book?

Bottom line, judging a book that was written decades or centuries ago by the standards of today doesn't make sense. That doesn't mean we still buy these books. However, students of history have to acknowledge that society looked very different in the past.