As of the end of the new Avengers: Age of Ultron, Natasha Romanov (a.k.a. Black Widow) has had an explicitly discussed romance with exactly one character, Bruce Banner (The Hulk). Among the precious few moments in the film that don’t revolve around genocidal robots are scenes of Romanov flirting with, pining for, and pleading with Banner; at one point—spoiler alert—she reveals that she, like him, can never have children. He's attracted to her, but he never accepts her advances out of fear of hurting her. Sex is not had.

So why do people like Renner say she's sleeping around? As Jen Yamato recently pointed out at The Daily Beast, the Marvel franchise has in fact used Black Widow as a tease for different characters in different films—a storytelling choice that stems, in part, from the fact that she's been the only female Avenger. When she’s introduced in Iron Man II, she’s an undercover legal aid who Tony Stark openly hits on before she surprises him with her combat skills. In the first Avengers movie, she acts as an affectionate confidante for Renner’s Hawkeye (a.k.a Clint Barton), though Ultron makes it very clear they were just friends. In Captain America: The Winter Soldier, she flirtatiously taunts Steve Rodgers, and at one point the two kiss for purely professional reasons. Modern-day fans of all kinds of pop-cultural products are famous for "shipping" any two characters with a hint of spark, and it’s no surprise Avengers viewers have done so with Romanov and her various buddies.

But Renner's “slut” joke isn’t an example of “shipping”—i.e. rooting for a romance to happen. It’s an insistence upon seeing a woman purely in sexual terms. It's also a rejection of the notion that men and women can have platonic relationships—that Smurfette could just be friends with the other 99 blue people in her village. Avengers director Joss Whedon recently spoke out against this idea when asked whether Hawkeye and Black Widow were ever meant for each other:

I find strong bonds between men and women that aren’t sexual not only cool and useful, but very romantic in a broad sense. There’s a lot of hate from the Clintasha crowd. It was never my intention that they were an item. I thought what was awesome was two people who would lay down their lives for each other who are not trying to sleep with each other. People keep saying that doesn’t exist, that men and women can’t be friends unless blah, blah, blah, and I’m just like, “Oh shut up.”

Critics of the Marvel Cinematic Universe have loudly protested the fact that Black Widow has been until very recently the only female superhero on screen, one who gets sidelined in the toy aisles and has been denied a standalone film. The case for more diverse heroes says, in part, that Marvel's diverse fans deserve and crave representation. But Renner's comments also underline the fact that it's also it’s just plain bad storytelling to have only one woman on the team. It makes the entire scenario feel even more far-fetched, it leads screenwriters to make her a potential love interest for multiple characters, and it encourages people to start saying weird, sexist stuff: No matter what else she does, the character's biggest distinguishing characteristic is her gender.