I don't hold it as axiomatic. You can read arguments for this position in works like On Liberty by Mill https://www.econlib.org/library/Mill/mlLbty.html . But it seems obvious to me that it is true in that if there is a single predominant channel of information, any disinformation propagated on that channel will gain much more credence than if multiple competing channels are available. For example, you can read on how the war in Ukraine in its initial stages gained popular support in Russia as a mission of liberation and "de-Nazification." In support of this propaganda effort, independent news sources were shut down.

You're right, but even researching deeply is not a true solution because of the forces that would have structured, unbeknownst to me, the archival materials available for my research efforts. Someone decided how large of a library to build and the librarians since chose which books and periodicals and reference materials to add to the library and which to remove and sell or destroy to make room or for other reasons. And the librarians purchased the things that they put into the library from distributors or publishers within which were other persons making editorial choices. And the authors of the works which were made available by the publishers, wherever and whenever they put pen to paper, were affected by the mores and views of their times and places and the availability of whatever kinds of information they wanted and needed to carry out their own work. It's turtles all the way down.

What has been going on recently on social media is a very different, very aggressive, hyper-invasive active version of this process.

We've been subjecting one another to the digital equivalent of having someone pluck a book out of your hands while you're reading it and pop it into an incinerator. Or doing the same to some of the magazines on the magazine rack you were walking towards. Or tapping you and another person on the shoulder on the sidewalk and telling you not to talk about what you were talking about anymore and placing a ball gag into the other person's mouth because he'd been warned to stay off that topic already and the thought policeperson knew or suspected that "garbage can lid" was a code word for "flat Earth".

Everyone has their own personal level of meddling and interference in their daily lives and interactions that they're willing to tolerate. Constant monitoring and modulation (even if it were truly well-intentioned) across most modern unencrypted forms of public and semi-public communications, whether it's centralized or whether it's been farmed out to certain departments in individual companies (which do coordinate with each other, outside organizations, and governments) is unacceptable and I will work around it or work to undermine it (legally) whenever possible and practical.