These days you have to go actively searching to find such on Freenet. And as journalists proved multiple times¹, if you do go searching, you’ll find a lot more of it in the clearnet via forums accessible with Tor than in Freenet.

And for the highest security in Freenet (the friend-to-friend mode), you need to have friends whom you trust not to go to lengths to spy on you — friends would be able to run statistical attacks if you transmit large amounts of known content. And such trusted friends are what people who want to access child abuse content do not have.

¹: Example (in German): https://www.youtube.com/watch?v=iItLpwkQMUQ