Oops! The search provider indexed it, and is serving it out to the world in the form of results. By duplicating your data without reading it, they're responsible. Jail for them.
Youtube and Blogger are a miniscule step beyond indexing. They're duplicating data you wrote on your computer, and serving it out to the world.
Content hosts cannot logically be responsible for user-submitted content. This leaves two outs: safe harbor, or only commercial content on the internet, so the buck can be passed (note that this is identical to a TOS). Remind me again where free speech fits in there?
edit: as I said in another comment: you don't put the papermakers in jail because someone wrote something mean on it.
A publishing platform can choose to be neutral (no power), or it can choose not to be. Of course safe harbour should apply to neutral media. For those that are not, however, I am not so sure. Almost, but not totally.
About the paper makers, you missed another point: anonymity. It should be very easy to reach the actual author of a paper, so this makes no sense to sue the paper maker. If the paper maker published all this stuff anonymously, and can't (or refuse to) disclose the author's name, however, that's a different story.
More-so than many other content-hosts, Google did act responsibly. If anything, Youtube is a medium just like the paper, but Youtube responds more rapidly and identifies criminals using the system uniquely, which is something paper cannot do.
Shall we eliminate all paper? It's easier to draw kiddie-porn on paper and post it up all over than it is to get away with it on Youtube.
Obviously, harboring criminals is different than helping an investigation to find the criminals. But without a takedown notice being ignored, there's no harboring, because there's no effective warrant. And without a legal takedown notice, there's no responsibility to remove anything, because to do otherwise would encourage people to restrict free speech just by complaining loudly.
Papermakers have the same measure of responsibility in this as Google. They can restrict selling paper to anyone until they see and approve the use of it, or stop selling altogether, or they can have a safe-harbor because they're merely creating a medium. If they sold paper to a book company that went on to write something which later got banned, they'd be in exactly the same position as Google, but nobody is saying we should all make paper ourselves, and affix our name and address to all the paper we make (running a server is easy to trace, telling who made paper isn't, so this is needed to level the playing field). And, as nobody can guarantee that that name and address are genuine on the paper, it cannot prevent anonymity, and loses significantly to a web host like Google who can point you to the source of everything they find.
Please, everyone, stop buying paper because people can abuse it. In fact, stop buying water because someone could use it to drown someone else, and the water company isn't doing anything to prevent this.
If we carry out this reasoning to its ultimate conclusion, platforms like YouTube or Blogger won't last long. It would indeed end the web as we know it. It will not end free speech on the internet, though. Not by a long shot.
Free speech can be achieved through two means: the out of jail free card, or a way for people to publish themselves.
Self publication is possible: we just need personal web servers, symmetric bandwidth, and the promise that we won't sue any ISP for moving bits (we need that safe harbour). Of course, companies like Google or Facebook prefer the out of jail free card (for many reasons, they prefer your data to be on their servers rather than on your own). I think the people will rather take the self publication route, given the choice.