That was a highly misleading article. Mastodon isn't a network, it's thousands of independent sites.
It's like the world wide web, you wouldn't hold Tim Berners Lee responsible because there are shady websites. All he did was invent the technology that lets anyone create a website.
If one server decides to do something terrible/illegal, the other servers block it and tell other servers to block it. That's why you cannot see these problematic servers from your server.