I can see why they found it sexist.
SPOILERS, BITCHES.
After having her breakdown and becoming as vulnerable as the other guys, she turns to a man and asks him to run away with her. Bruce wants to be stoically alone, Tony wants to work with his hands, Cap wants to have an exercise, Thor wants to go through a spiritual journey, Clint hooks up with his family. But Natasha?
She turns to a man to whisk her away. She opens up to him-- an act alone actually a display of strength-- but immediately asks to run away with him. She doesn't deal with being shaken up on her own like the others; she doesn't dig deep and stand back up. Ultimately she does keep fighting, but even at the end, she wants to run away--
With a man.
That's why they see it sexist.
Okay. So if it was man doing that, would it be sexist at all? Because there are plenty of moments in film of men wanting to just run away too. Even to run away
with a woman to have kids instead of dying in some horrible conflict.
Again, I think the character could have been handled better. I would have liked to have seen her get
something to put her on the same level of power as those around her, but let's look at things from her perspective for a minute here:
She's basically fighting a war surrounded by demigods as a puny human with nothing more than a gun and the ability to fuck with people. Then along comes Scarlet Witch, who can do what she can do
except on mental steroids. Wouldn't you basically feel
useless and powerless, and want to run away? Start a family? Not become a nameless fatality in the middle of nowhere, not being able to do anything because you lack the superpowers that seemingly everyone around you has?
If anything, I think this is probably the most human moment that Black Widow has ever had in the two films thus far. Except,
because she's a woman, she's not allowed to be weak. She's not allowed to want to run away. Why? Because that's sexist now. Completely forget that Scarlet Witch was in the film doing badass shit, no, we have to focus on Black Widow--a horribly underpowered, fleshy human--wanting to run away.
I will grant that from their perspective, it
does look sexist, but when I put myself in the shoes of Black Widow--I would want to run away too. I'd be massively underpowered for what's going on around me. Throw in Scarlet Witch, and, well, there you go. Plus, make criticisms about the character all you want. I think she could have been done better, but I'm not going to call Joss Whedon a sexist for allowing a woman to show weakness and desiring to run away.
Especially when there is another female character in the film who commands respect through sheer power.