Why not analogize to murder in this particular respect? (Though let me be clear that my analogy is fully constrained to what follows.) Let's not go through all the potential causes or rationales for killing another human, or the special cases (e.g. capital punishment, assisted suicide, etc.). Suffice to say that killing another human is only even slightly tolerable if it is considered to be in self-defense. Accidental or negligent killings, then, are somewhere between that and full, heinous, murder.
So, then:
Is there such a thing as rape in self-defense? No, come on - that's silly.
Well, if the victim of murder or manslaughter is not considered to have been "asking for it", then how could the victim of rape be so?
Now, "asking for it" refers to either secretly wanting "it", or else to having in some sense 'brought the outrage upon oneself'. I can't address the former interpretation head-on, but for the latter we may return to murder.
Simply put, no victim of manslaughter or murder is considered to be responsible for their fate legally-speaking. This is so even if their interactions with the perpetrator prior to the crime were much more active and threatening than is usually the case with rapists and rapees. For example, if I insult you and urinate on the couch in your home and you gun me down for it, most would feel quite uneasy to say that I "had it coming". And again, with rape all the victims are said to have done to the perpetrator (for this particular subset of cases) is "tempted him".
Think of how shocked we the public would be to hear of a case in which someone's excuse for murdering someone would be "they was dressed like shit and they looked at me funny". We'd likely conclude that this individual should be sequestered away from the general population. It would be difficult to find apologists.
Summing up:
- Rape can not be in self-defence.
- Killing is not an acceptable response to provocation.
- With rape, if there is any provocation involved then it is surely usually of a comparatively-passive sort.