"Chilling effect" has always been a profound term for me, because I imagine the "cold" (numbness really) sensation a human body often senses when something truly awful (disembowlment/dismemberment) occurs. The body's way of protecting itself is to go "cold", and in many ways that's exactly the effect taking place here, as well.
There's also an undeniable part of this conversation that rarely gets addressed simultaneously, and I'd like to see it sussed out more in concert; what about the folks who are doing Evil in these private channels? It's unacceptable to me that TOR gets used for child pornography, and it's unacceptable to me that my government finds out I'm gay before I come out to my family.
I don't want to provide those who would do Evil any safety or quarter. I also want to give people a powerful shield to protect themselves against judgement and persecution from the public and sometimes the law.
We should talk about achieving both of these goals, but we generally don't.
However, the true wins will come by doing real-world police work, educating parents and children on how to protect themselves and what are the potential offender profiles (hint: not guys in an ice cream van). They will come on a diplomatic level by negotiating better laws in countries where such materials are produced (Japan was a recent success AFAIK) and where sexual tourism is rife.
Finally, those individuals that haven't abused anyone should receive support from a mental health specialist if they come forward and admit to their urges, like in e.g Germany.
I have the feeling that this is a taboo subject, that is not discussed frankly in most societies. The authorities focus mostly on harsh punishments instead of prevention through education and mental health treatment.
Thinking about what happens on tor is mostly a reactive policy that doesn't do much to treat the causes.