You have to go out of your way to find abusive media on freenet. There are many top lists of freesites and they are censored of abusive media. I recommend FMS the freenet messaging system which uses web of trust successfully to moderate messages in a Usenet forum.
Out of curiosity, what sort of things are on freenet? Is it worth installing it in a Tails VM?
It's incredibly slow (think Tor over Tor over Tor), and needs to be run for 1-2 weeks to even work mildly. Tails would not be an ideal choice, a dedicated space is necessary.
There's no real reason to use Tor to connect to Freenet anyway, as it's encrypted in a way that the network traffic cannot be known nor even the content on your machine by yourself unless you know the private key which serves as a link to the content you are trying to locate, and it eventually will sync up those keys with your local storage. You don't even know the public key of the content that is stored in this local cache.
If you've seen Silicon Valley, this is the idea that likely founded "the Platform" concept, but they add a bit of magic and speed to the concept for the show. When your content is published, it's published "everywhere and nowhere". If you publish something, then destroy your node, that content will stay in many nodes and still be accessible. This information gets kept or cleared out based on how often it is being queried.