Actually, everyone's afraid of guns. You'll stop most criminals just by showing that you have one. Don't even have to draw it.
Look at the states in the US where right-to-carry laws hold. Violent crimes are cut by half in those states, in comparison to population.... the criminals are too scared to act. Of course, it doesn't have much effect in stopping the most common violent crime- which is from people you know personally.
Training to use the weapon, however, is the thing no one ever appreciates. A knife or gun in an untrained, frightened, person's hand.... might as well not even have a weapon, it's safer just to let the attacker have what they want and leave. Most rapists are criminals of opportunity, and very few of them will hurt the victem any more than what is necessary for their goals.
However, a gun being held by someone who knows they can hit a target.... you'll never need to fire a shot. True, if you're up against a gang of people, you can't shoot them all. But there aren't many who are eager to be amongst the ones you DO hit.
