It's easily to design solution that will work around and allow sending either criminals or kids nude pictures under the radar, e.g.
1) Someone will eventually write web app that will use webrtc or similar for snapping nude picture (so that no picture is stored on device) 2) encrypting those photos on the server 3) sending the link to this nude image that will be rendered in html canvas (again no image will be stored on device) 4) link to web app that will rendered image will be behind captcha so that automated bots cannot scan it
Now do we want to go into the rabbit hole to 'protect the kids' and make Apple buildin camera drivers that will filter all video stream for nudity?
Sometimes otherwise good, smart kids, with good parents, can be caught up by predation. It isn't always as simple as making sure the kid is educated; they'll still be young, they'll still be immature (< 13!), and it will sometimes be possible to manipulate them. I'm not saying that what Apple is doing is a good answer, it probably isn't, but it's an answer to a genuine felt need.
But if I'm picking a phone for my kid, and my choice is this (even if imperfect) and the HN freedomFone - it's going to be Apple. We'll see what other parents decide.