Derek Savage's suggested scenario to deter a would-be rapist is highly implausible for a number of reasons.
(1) Savage's inference that a gun left in plain view on a car front passenger seat is not a proper place to store a handgun when not in use, especially if/when a car would be in motion, where a gun could potentially fall off a seat (imagine needing to hit the breaks in case of a sudden stop) and unintentionally misfire, which could injure the car's driver, other car passengers, or even another driver or pedestrian around the car, as well as damage the car itself.
(2) If a firearm is left in such a place while a car is unattended, anybody else passing a parked, empty car could easily break a window and help themselves to a free, loaded gun. Even a potential rapist or other violent criminal (as in Savage's own scenario), while scouting targets, could potentially notice a gun left in a car, and before their victim returns, the violent criminal could just as well steal the gun in order to use it against their target upon returning to the car.