You raise a good point. There is a difference, however; the Internet is actively monitored and ISPs respond to/work with the police to reduce this kind of content. Can the same be possible on something like Freenet?
The real problem here is child abuse, and people should focus on this. Sometimes I think that actually our society don't really care about the children: it's more like they just don't wanna know and that's why the common answer from the govt is "filter the Internet". IMO the best we can do is think how we can find the child being molested on certain pic, not trying to figure out some magical way to stop distribution, because if we keep trying this we're just wasting the(ir) time...