A motivated attacker isn’t going to be deterred by anything less than using more force against him than he is willing to experience. Rape whistles, yelling the word “no”, or racking a pump shotgun WILL NOT deter a motivated attacker. For that job, ruthless violence is the only solution.
Force disparity matters. And really, when it comes time for you to defend your life, you want the long-end of the stick. As Greg discusses, it’s what works.