I'm confused, are you saying that it was the 11 year old girl's personal responsibility to avoid being the victim of sexual abuse? Or are you saying that it was her parents' responsibility to be monitoring her technology use 24/7?
Neither seems right to me...
Now the predators will just continue to do there thing in a darker hole that is even harder to find.
If it's harder to find, then fewer children stumble upon it and get preyed upon, which is a good thing.
100% monitoring and control doesn't exist. Your children will find a loophole to access unrestricted internet, it's what they do.
Similarly, children will play in the street sometimes despite their parents' best efforts to keep them in. (And yes, I would penalize Ford for building the trucks that have exploded in size and are more likely to kill children, but that's a separate discussion.)
I get what you're saying, I just think it's wrong to say "parental responsibility" and dust off your hands like you solved the problem. A parent cannot exert their influence 24/7, they cannot be protecting their child 24/7. And that means that we need to rely on society to establish safer norms, safer streets, etc, so that there's a "soft landing" when kids inevitably rebel, or when the parent is in the shower for 15 minutes.