This really makes no sense. What happened to "innocent until proven guilty"? Plus, how is the accused meant to prove consent? I doubt anybody reads and signs a binding contract beforehand.
In cases of sexual crimes you will never be seen as innocent. Even if they find out the claim is false or you're found not guilty expect society to immediately treat you different. I've read the accounts of those that this has happened to, and the purveying attitude towards them isn't "wow, she was crazy and I'm glad the justice system did right" it's "you got away with it". One guy was beat bloody on a sidewalk when it was found he was not guilty when the girl admitted it was a false claim - the assailant believed she was coerced.
Unfortunately, the assumed victim in the case can have the benefit of anonymity but defendants do not receive the same protections so even when found not guilty the societal stigma remains. Even if you go back to court and fight for an innocent verdict and are granted it (yes, this does exist) - you still are likely to have issues. When a simple Google result can find you involved in a rape case at a potential employer it's easier for them to simply not hire you for perceived risk of litigation should a sexual harassment lawsuit be pressed.
Yeah it is a massive problem. There's also the whole "vigilante justice" aspect, where people will get their property destroyed or even killed before a judgement is made. I've also seen what happens and it is saddening. It doesn't help that men are also always seen as just the rapists, when there are a large number of unreported male rapes every year.