So the author wants to protect "the marketplace of ideas" from monopolies caused by a different market. However, they don't want the government to do it. They also don't seem to think it's possible for smaller companies to challenge these monopolies. What then is the author's solution? One is never given.
In my opinion, the solution is simple: If any “platform” censors beyond removing illegal or copyrighted content or spam, they should have their “platform” status revoked, and they should be considered a publisher. This prevents such companies from using “platform” status as a cost saving mechanism to help them become large monopolies. Companies like Facebook would not have been able to take over so much of the market…
The second is that Facebook doesn't have to censor you to censor you. They just tweak your post so it stops showing up other peoples feeds. Youtube does this all the time, they don't censor anyone, they just make sure no one can find the voices they don't like. Meanwhile the content they like gets boosted, we've seen this all the time where you go to youtube for a video about puppies and thanks to autoplay 4 hours later you're hearing about how feminists are destroying western civilization from within by Jordan Peterson.