This would work if we all were reasonable human beings, sharing a common set of values and following a just moral code. Unfortunately, we are not. Rape is not an act of sexual attraction, but one of power. Begging will do little more than entice the attacker, as this is what he wants. This confirms what he wants to believe and is out to prove through subjugating his victim.
I would say ask the victim of a Canadian rapist who filmed his victim begging for her life after she had been raped over and over again. He filmed his repeated assaults upon her until she finally just begged him to tell her mother she loved her. I would say to ask her but you can't. She is dead.