People in general already know that it's wrong to rape. It's a class A felony which can land you in jail for a decade. Anyone who is accused of rape —even falsely — has their reputation tarnished forever and their lives irreversibly ruined.
Nobody is under the misapprehension that rape is a good thing. We know that it's bad, but in the same way that thieves know it's wrong to steal and murderers know it's wrong to kill, rapists know that rape is wrong yet do it anyway because they don't care and they believe they can get away with it. That's how criminals are.
And this isn't just idle speculation. The Rape, Abuse & Incest National Network (RAINN) will tell you that rape culture is imaginary and rapists rape despite knowing that it's wrong. Speaking on the subject on the rape on college campuses, in a letter to the White House in 2014, the largest anti-sexual violence organization in America warned:
In the last few years, there has been an unfortunate trend towards blaming “rape culture” for the extensive problem of sexual violence on campuses. While it is helpful to point out the systemic barriers to addressing the problem, it is important to not lose sight of a simple fact: Rape is caused not by cultural factors but by the conscious decisions, of a small percentage of the community, to commit a violent crime.
You can't teach somebody who wants to commit a crime to not commit a crime. That's why we have police and prisons. To refuse to take precautions against being raped on the grounds that men should know not to rape is just as idiotic as refusing to put locks on your doors on the grounds that people should know that going into some else's house uninvited to steal things is wrong. No; that statement is not "victim blaming", nor is it excusing rape: it's just common sense. I'm a guy, but even I wouldn't feel safe walking unarmed down a dark alley in Detroit at 3 AM.
It's not your fault if you get victimised, but you cant reasonably expect to not be victimised when you enter into a situation where it's likely to happen, you don't take any steps to prevent it and you actively advertise that you're an easy target. A criminal isn't going to stop victimising you just because you tell them that it's wrong, and it's moronic to think otherwise.
The "teach men not to rape" rhetoric presumes that men somehow don't know that it's wrong to rape. As if we are savage animals that need to be trained. It's a demonising idea that implies that all men are inherently perverted rapists and the only thing stopping us from committing despicable acts is a social conditioning. It's unfair, insulting and fear-mongering. It's the type of attack that makes women afraid of men, and it contributes to the growing atmosphere of men being afraid to even talk to women for fear of being accused of sexual harassment.
While rape is a serious concern on college campuses, the obsession to combat it has created what a Harvard Medical School psychologist William Pollack describes as a "witch-hunt" environment, saying "we’re starting to scare the heck out of the wrong people".
The perpetuation of the idea that a rape culture exists is actually very harmful, as RAINN writes:
This has led to an inclination to focus on particular segments of the student population (e.g., athletes), particular aspects of campus culture (e.g., the Greek system), or traits that are common in many millions of law-abiding Americans (e.g., “masculinity”), rather than on the subpopulation at fault: those who choose to commit rape.*This trend has the paradoxical effect of making it harder to stop sexual violence, since it removes the focus from the individual at fault, and seemingly mitigates personal responsibility for his or her own actions.
Women shouldn't be made to feel afraid of men, and men shouldn't be made to feel like villains when they've done nothing to deserve such condemnation.
The "we need to teach men not to rape" argument is stupid because it's a blanket condemnation of men which perpetuates fear among both sexes, and appeals to a very unhealthy, backwards mentality which could only result in further victimisation in the long-term.