It wasnt till I read your take on the poster that i saw that point. Whether you like the fact or not, the poster its a warning, just as a warning sign in a subway about pickpockets is a warning. You never think when you see that sign that 'oh yeah sure blame the victim'.
To be honest there is a far way from blaming the victim here, although I agree that is generally is a problem. Here its simply an overreaction...
Googling pickpocket signs, they all say something to the effect of "Beware of pickpockets" or "High risk pickpocket area". One said "The world's best pickpockets are here. Stay alert." Even the one that came the closest to being a parallel poster said: "Warning - Thieves operate in this area. Keep handbags - purses - wallets safe"
So if we are to use the pickpocket warnings as a guide, the OP sign should actually read: "Warning - rapists operate in this area. Stay alert to keep yourself safe."
Do you see the difference?