This concept is already enshrined in law, the concept of free harbor. So long as a service provider doesn't do their own curation, they are not held responsible for the content that is posted. However, if they do curate, then they are responsible.
Applying this to Twitter, Facebook et al. is not that big of a leap.
> completely destroys the business model of several hundred billion dollar businesses
They are not entitled to their business model, especially not at the price of trampling upon something broadly considered to be an inherit human right.
