HN user
If they can’t exercise effective editorial control, they shouldn’t be in that business. Same as a newspaper that publishes harmful or libellous content. Will it kill off Facebook and Twitter in their current forms? Probably...but that’s a feature, not a bug.
Social platforms need to be held legally liable for the content they host. Unless you’re a “dumb pipe” doing one-to-one comms (email services could get an exemption for spam filters), you’re a publisher.
Hire moderators and the editors. If that doesn’t scale, then you need to cut back on the user-created content you host.
The content can be shared in other ways via the internet, but networks inside the network shouldn’t get a free ride anymore.