To what extent is a rape victim responsible for the crime?

[kılıç_mehmet]

Reality is that some rapists do actually have preferences in their victims.
Most of these look for a women that they think is of a "lesser reputation", meaning, doing or wearing things that represent this.

So rapists might target people they perceive as more vulnerable. And this make it the victim's fault, how?

Not all, some rapists. Especially those who target people who they don't know personally. Those who do, don't need to skulk around and look for vulnerable victims, they already know when their victims are the most vulnerable.
Though for the type of rapists who are predators by their nature, they seek out victims that are snatched away easily. There is fault, I never claimed that. But irresponsibility, there is of course. We know that the streets are not safe from such individuals. So women must be on their guard, and go out at nights with at least one friend to ward off such attackers.
For being the victim's fault, I don't think that this nor anything else can be used for the defense of the attacker in the court. The crime is determined, and its circumstances are known. So what is there to determine about the fault of the victim?
Like for example, I know some people blame victims for their dress, yes it could be provocative, and I personally do not endorse such ways of clothing oneselves, yet this is not a valid defense for the attacker.
It would be as to suggest that a person who was mugged was at fault for looking "too wealthy".

However as long as good people leave themselves vulnerable to attacks, they are prone to getting attacked. For example, it is never a good thing for a girl to hang out at disreputable places of debauchery and drugs. If she gets raped, although the rapist is the attacker, the has put herself into danger by going into such places where one could expect a drunk or drugged person or even a bunch of drugged or drunk people to sexually assault someone.

So it is to say, that people who wish to avoid the danger of rape, should either travel around with friends, or not visit places where they could expect an attack. It is in their responsibility to take precautions for their safety, and in the case of a crime, it is the responsibility of the state to punish the perpetrators.