The Onion

In your first examples, you are using female as an adjective. A female troop, a female Sargent, a male soldier. That's usually fine. Even "that female cashier over there" is probably fine. However if you say "that female over there" or like you pointed out, "get over here right now, female" or really any other instance where female is used as a noun instead of an adjective, that's where it becomes gross. It's all about adjective vs noun. Adjective: usually fine. Noun: usually not.