While I agree you shouldn't be able to sue service providers, I think it is different because Twitter and Facebook recommend things for you to read and amplify the message.
The recommendation/amplification aspect is what needs liability.
It isn't their job --at least not what I think the job the US Constitution should protect-- to create their own version of what he said, embellish it or modify it in any way, in support or opposition.
I don't want news anchors to creatively interpret reality for me. I want facts. The interpretation is mine, not theirs. Most of them are politically biased liars.
In other words: they aren't expected to have actually read every word of every book they sell. Publishers, newspapers, etc, are. But if a book defames me on page 154, the law doesn't hold the bookstore responsible unless it knew. Once it does know, you could probably sue. But that's not the same as treating it like a publisher- it's a different standard.
It doesn't appear that they even have a duty to the buyer for it to be a good and useful work.
The duty you want to imagine is real would seem to be impossible to reasonably provide because the cost of paying out every time they were wrong would mean books would all cost $500 and in turn the book stores would all shut down. The only viable way to sell books would be to run a website overseas in a less insane jurisdiction selling epubs.
If you wanted to take it to the next level and enforce liability for anything that goes over the wire you could just give up 99.9% of content in the universe?
profit motive for recommendation/amplification is probably what damages humans at scale