It's not about blame. If someone drugs and/or rapes someone else, that person is to blame. But it is possible to avoid situations where you're vulnerable.
Taken to the extreme, never get in a car because you can get in a car crash. Never go on a plane because it can crash. Don't send your kids to school because they might get shot.
Many people used the couch surfing website and did not get raped (the vast majority). Many people have been raped in ways completely unrelated to couch surfing.
Such "advice" really isn't helpful.
Also I'm not arguing for avoidance of all risk. If people want to do risky things, fine. Heroin, BASE jumping, staying overnight at a stranger's house -- have at it. What I'm objecting to is the idea that there's something wrong with giving people advice about the potential danger in certain situations. There isn't!
We can ensure our safety, or we can live our lives and experience the world. Perspectives that jump instantly to what a victim could have done better to improve their safety are reasonable, especially when discussing prevention, but you might learn something about the very common angle of these perspectives if you consider other situations re: personal security where you don’t immediately ump to what the victim could have done.
My observation is you get a LOT more of the “oh you silly thing, how could you have not known this would happen to you?” When dealing with female victims of sex crimes.