INT. ARMY BARRACKS - DAY
A group of soldiers climb out of their bunks, and look around the hastily constructed army tent that serves as a barracks. None of these people have met each other before. A cigar chomping, probably black, COLONEL enters.
COLONEL
Alright listen up. I've got you together
because you're the best of the best.
One of the soldiers, an obnoxious, stupid looking, buff one, puts up his hand.
COLONEL
What is it, marine?
STUPID MARINE
(pointing at a female marine)
Since when do we work with giiiirls?
The female marine smirks at the put down. Everyone rolls their eyes, but watches to see what happens. The female marine, smiling demurely, approaches the stupid marine. She is shorter than him, but clearly hard as nails herself. Without warning, she punches him hard across the face, knocking him to the floor. Everyone laughs, including the probably black Colonel. The stupid marine crawls off without a word, humbled. The female marine spits in a masculine way. Sexism is defeated.
END SCENE
So what's wrong with this scene, apart from it being a horrendous cliche that crops up in a dozen different variations, is that it insults everyone's intelligence. The audience these days (for the most part) respects women and stories enough to accept that there are female soldiers, enough that we doesn't need a demonstration every time to assure us that, yes, women can be as tough as men. The only way this scene can happen is if the story requires a ridiculously idiotic moron character to make overt sexist statements. This means that whilst the message may have meant to have been "don't say sexist things about women", no one relates to the big idiot. They don't see themselves making such stupid statements, so they go on to assume they are like the rest of the soldiers, and totally not a sexist. Meanwhile, things like implicit sexism, or the suggestion that even intelligent and well meaning men can have demeaning or quietly sexist attitudes that you can't punch, doesn't enter the picture. It's sexism for children, but in a militaristic setting aimed at adults.
It also means that these female characters are usually portrayed as hyper aggressive. If they don't like something, they punch it. They go way too far the other way, constantly asserting how tough they are, to the point where it starts to make them look really insecure about themselves. It puts these women in a position where they can't win; either they concede that they are somehow weaker than men, or they look like they are desperate to prove they aren't.
So how to avoid it? Don't have it. At all. Look to the most recent female heroes, like in Mad Max: Fury Road. At no point does Furiosa ever have to assert her own position. There is never a scene where someone doubts her ability, and there is never a scene where she has to slap them down to prove it. Alternatively, there is Wonder Woman, which takes the complete opposite approach. In this setting, literally every male character is a sexist who spends the whole movie trying to tell Diana what she can't do. Even Steve Trevor, the nice guy hero and love interest, gets in on the act. He, more than anyone else, undermines her power and authority, thus showing that even the well meaning, sensitive and intelligent people will still have their prejudices. Diana does not have to get physical with these people though. Instead, she is so self-assured and so much better at what she does than any of these guys, she marches up and does it. Now that's powerful.
