As big a problem as any in our civilization is the obsession with punishment and neglect of prevention, mostly because it rarely if ever occurs to us that there are more effective ways to deter behavior than just handing out the worse possible sentence to every perpetrator.
I believe that fear is a powerful driving force and deterant.
If people see severe and brutal punishments dished out for rape, they come to realise how despicable the act is once they realise that they can't argue that they wouldn't appeal for the same punishment if they, or someone they care for, where the victim.
Frat-boys would soon realise that getting to know a girl, is preferable to slipping one a roofie and than getting shot on live television after the trial.
Edit:
Also, I feel that there is little to do to prevent such an act. It's pretty much forced down our necks that "No" means no, and that "Rape is wrong" due to it being covered in sexual health at school, and by the media.
Isn't rape usually about exerting totall control, rather that sating lust? So surely a punishment that ensures that the perpetrator will never be able to control anything, and knowing that their life will end at the hands of another, would be the most fearsome punishment.