It's you versus him. No one else is near enough to hear you. You're trapped. In the millisecond you have to decide you can't tell what his intentions are - simple rape or something much worse?
You have a moment to place a loaded revolver in your hands and shoot. Do you?
They get angry. They get flustered. They don't want to hear it. No matter what, it forces them to think.
The most common goofiest answer is something akin to “my gun will just make it worse [for me].”
The more common answer would be to deny your scenario out of hand. They’ll say they’re blahdeblah percent more likely to shoot themselves or a loved one. And maybe they’re right, I don’t know. Certainly having a gun has to up your odds of being shot, just like how were I never to drive or ride in a car I’d cut down on my odds of dying in a fiery wreck.
For some reason our civilization is comfortable with the awfully bloody risk of automobile travel. We’ve seen the benefits and aren’t willing to go back to animals. Most people can’t see the benefits of guns, and wildly overrate the risk.