Their job is not to control the internet

They take websites offline if and only if they receive a legal order to do so.

Sites with user generated content have broad protections against illegal actions of their users unless they do one of a small handful of things that exposes them to liability, like actively participating or ignoring legitimate takedown requests. It's not an accident. That's how the internet is intended to work, and the only way allowing user generated content is realistically possible.