Yes, the public Freenet opennet contains lots of horrible content. But then, Freenet's focus has always been censorship resistance. Content gets distributed and replicated according to its popularity. It's a lot like BitTorrent, but with serious transport encryption and randomized routing.

And arguably it's worked pretty well for that, given that there's been consistently lots of horrible content for 18 years. Content providers (and users) have been busted, but that hasn't eliminated much of their content.

However, being a pure P2P system, you only have "anonymity" through plausible deniability. And that's a dangerous game to play. Criminal investigators have used modified Freenet nodes to track chunks of illegal content, and have prosecuted users whose nodes processed those chunks.

The Freenet Project argues that it's impossible to reliably determine whether nodes are requesting those chunks, or merely relaying requests from other nodes. But if you end up in court, you'll need an expert witness to convince the jury of that. So you'll likely end up with a plea bargain.

So anyway, it's safest to run Freenet on anonymously leased VPS, and access its webGUI as a Tor .onion service. Just as you'd prudently run a BitTorrent seedbox.