"I think it generally means killing female heroes is supposed to elicit more emotions from readers than killing male readers. (...) I think the wholesale slaughter is because there's a lot of writers who think all major character motivation is made by killing folk and women characters are easier to kill than male characters since so few of them are major heroes on their own. (...) I fear, that most boys want to read stories about big muscled guy heroes showing off than gal heroes. They want the girl heroes there in the background, and even important to books, but they rarely if ever buy a book starring a female. Younger boys I think are frightened to some degree by the overly muscled women even while they may find a sexual delight in them."
January 1, 1970
https://en.wikiquote.org/wiki/Women_in_Refrigerators