A sexual attack sullies the victim
Because rape is seen as sex rather than violence, and a womans' sexuality is still seen largely as the property of her present or future husband, a rape victim is seen as having been 'spoiled' or 'dirtied' by an assault. Among Muslims, for example, a woman who has been raped is sometimes disowned by her fiance or family for having brought them shame by becoming sullied and thus unmarriageable. St. Vincent's Hospital Rape Crisis Center in New York has had to shelter rape victims from the threat of murder by their families for these reasons. Victims of nonsexual crimes are never seen this way.
Rape is a punishment for past deeds
This myth applies to all sorts of vicitms, both of crime and accidents. It is as ancient as the idea of fate itself, yet plays a living part in people's thinking about tragedy. The myth may be a defense mechanism; if we believe that victims bring on their misfortunes because of past bad behavior, then we can convince ourselves t hat we are immune by virtue of having been 'good.'
Women cry rape for revenge
The idea that women like to use accusations of rape as a tactic for revenge has been popular for thousands of years. In Susan Brownmiller's definitive history of rape, Against Our Will, she pointed out
The most bitter irony of rape, I think, has been the historic masculine fear of false accusation, a fear that has found expression in male folklore since the Biblical days of Joseph the Israelite and Potphar's wife, that was given new life and meaning in the psychoanalytic doctrines of Sigmund Freud and his followers, and that has formed the crux of the legal defense against a rape charge, aided and abetted by by the set of evidenciary standards (consent, resistance, chastity, and corroboration) designed with one collective purpose in mind: to protect the male against the scheming, lying, vindictive woman.
The tendency of women to lie about rape is vastly exaggerated in popular opinion. The FBI finds that 8 percent of reported rapes are unfounded, but other researchers put the figure at only 2 percent.
One function of all these myths, and perhaps the reason they persist to this day, is to protect non victims from feeling vulnerable. If people can blame a crime on the victim, then they can find reasons why that same crime will not happen to them. A way to do this is to subject the victim to a set of old-fashioned moral standards for more rigid than are normally applied in everyday life, so that the victim is bound to fail and look like a 'bad' woman.
...from Virgin or Vamp: How the Press Covers Sex Crimes, by Helen Benedict.