The glorious moment a sports fan is called out for sexism by the stranger next to him.

As women, we often find ourselves in the presence of blatant sexism, and are at a loss for what to do.

Much of the time we stay silent and ignore it, frustrated we have to witness it in the first place. But a US woman who watching an NFL game has given us a masterclass in how to call out inappropriate behaviour when we see it.

In the video above we see Buffalo Bills coach, Kathryn Smith, walk out from the changerooms when a spectator begins to yell.

“Waitress!” he calls aggressively. “WAITRESS!”

Smith ignores him and continues to walk towards the field, concentrating on doing her job rather than engaging with the rude, sexist guy in the stands.

But the woman beside him (who supports the same NFL team as he does) makes it clear that his behaviour is entirely unacceptable. At first, she covers her mouth, and it looks like she’s trying to calm her fury.

And then, she decides she's had enough.

She hits him on the shoulder and just says 'no,' while shaking her head.

He looks at her, turns the other way, and stands with his back to the camera.

A straightforward "no" is a simple move, but an effective one, and it reminds us just how powerful we can be when it comes to calling out unacceptable behaviour.

We'll definitely be channeling this woman the next time we find ourselves frozen in frustration, because the more times we blatantly say 'no,' the more we'll force these types of people to think about what they're doing.