My grandma find politics very disgusting and discussing it would mean the same as CP for you. She is from ex-USSR. Does this means we should ban politics in darknets too?
And it is your approach is naive. You ignore technology. You can not technically limit information propagation in any kind of network. It will find a way. But if people will think that the only reason to go to any time of crypted network - is to fetch CP - here we go - society prepared for laws preventing cryptography (you can be imprisoned in UK for not giving crypto keys for a several years!)
Again - we might want to work on technology recognizing nudity, or abuse or whatever and protect ourselves and our kids or our moms from this type of content, but this should be completely separated from technology used to share this data! Just like there are parts of big cities which are not safe for white/black/chinese/etc guys. It doesn't mean we have to put tall wall around this part of city. Instead whoever think it is not safe there - just do not go there.
Want something to be used? You have to think about user experience. You have to think like a marketer or a designer. What I see here is a lot of people evading the issue because it involves human beings. Technologies do not become popular until somebody includes the user in the design equation, and only popular technologies have large impacts.