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.
Latency is typically high, but the browsing experience is pretty good.
The content of those sites is whatever their authors want it to be :)
Further, dynamic applications such as forums are also available. Here's a list of apps built on top of Freenet: https://github.com/freenet/wiki/wiki/Projects
Freenet needs UDP so it likely won't work on Tails as Tails tunnels everything through Tor - which does not support UDP AFAIK.
[0] https://bluishcoder.co.nz/2016/08/18/using-freenet-over-tor....
So you can only connect to Freenet with this setup if you already know someone else who uses Freenet and peer with them manually ("darknet").
A network vending child pornography should not be happy about this. This should be a terrifying warning to you.
Unfortunately you don't see it as a genuine problem, so you explain it away.
bad developers that make excuses for a network that won't stop the delivery of child pornography by hiding behind false ethical arguments