How are you supposed to train the dam thing to detect something without using that thing though?
There are various organizations which have clearances to handle child abuse images. Where the data is handled like the plutonium it is, and everybody is vetted. I'm sure they've already experimented with developing a bot to detect images.
They even make available their traditional hash databases to server admins who want to run their images against their hash databank.
The issue as the report states is that nobody will willingly link said bot/database to the training data, because either they don't want a copyright fight or they don't want to acknowledge the issue.
No, people writing about sexy stuff and getting paid is worse than Nazis making money.
Edit: Being fair, the bible thumpers of old who established all the laws/morals which underlie most of the regulations today would take a big big problem with people writing sexy stuff. Nazis hating Jews would not be a big problem for them.