Is culpability absolute or is there a sliding scale? Can the victim and the perpetrator share culpability? If commission of 1 crime always results in 1 culpability, but the perpetrator is only responsible for .8 culpability who owns the rest? What about in a 50/50 situation?
Homicide law in the western rules reflects a wide variation in culpability as reflected in the types of murder: homicide, manslaughter, 1st degree, 2nd degree, involuntary, self defense, and so forth. These categories are broadly differentiated by the legal terms intention, knowledge, recklessness, negligence.
Contrast homicide with rape, where discussion of variable culpability in the context of rape is constantly derailed. Now, don't misunderstand. More than anyone I have very good personal reason to oppose rape and rapists. The idea of the possibility of a lesser sentence for a crime that I consider to be worse than murder gives me a sour taste in my mouth.
But if we are to rationally examine something we have to set aside emotion.
It seems quite reasonable to say that anything that applies to one person, must apply to all. If a woman sexually cannot consent if she's consumed alcohol, then neither can men. If sex occurs in that context, is it rape? It makes no sense to say that neither party consented to sex despite the bald fact that they had sex. But it also doesn't seem right to say that rape cannot occur due to inebriation. Perhaps a middle ground is needed. Or like in drunk driving law, argue that people are still responsible for their own actions, but the legal penalty is lessened.
The legal definition of rape is when there is sex by force, coercion, or constraint. Currently a person can be convicted of rape where none of these things were present. Perhaps such a person is indeed a rapist. But not to the same degree of the rapist who with premeditation forces violent sex.