Facebook and Google occupy a legal grey area between publisher and common carrier that was literally created by the CDA. So your argument is like saying, "Vaping has to be legal because how else is Juul going to stay in business?", or "Loot boxes have to be legal because they're so important to EA's and Activision's business model." These companies only exist because of a certain legal environment, so how can their existence be used to justify that same environment? Are Google and Facebook now considered inalienable human rights used to derive laws?
Maybe Google and Facebook would be able to survive a change to the CDA, or maybe not. Who cares? The internet ran just fine before the CDA and the technology hasn't really changed much at all. Heck, the two of us are conversing right now without Google and Facebook involved.
Everyone gets so bent out of shape these days about Google and Facebook but no one is willing to even imagine an internet without them. Present company excluded, of course -- at this point I'm just ranting.
> A newspaper would be different if it published every letter to the editor it received, so long as it didn't contain the words "child porn", for example.
This is not true. It has nothing to do with the choices of the editor and everything to do with the medium used. The CDA carves out a specific immunity for internet companies that does not apply to print and broadcast media and that's what Barr is putting on the table here.
Is Facebook responsible for every word of every Facebook post? Have they decided whether to publish it or not? No. (Yes, they do have certain filters that try to exclude certain things, but that's all. A newspaper would be different if it published every letter to the editor it received, so long as it didn't contain the words "child porn", for example.)