OK, that's at least a more reasonable thing to be worried about [0], but as you say trying to use the law there would be damn near impossible. Take the case of a law against airplanes/cats again. I'd definitely feel very, very strongly about such an effort, and want very, very much to defeat it. In the democratic system that means rallying a critical mass of fellow citizens. If it so happens my airplane/cat platform is pretty popular and likely would share my interests amplifying that would be a reasonable way to go about it, using algorithms that optimize for results. You might say "well, commercial use restricted only" but how would that be different the typical ad testing runs which have existed forever, where they are constantly testing to try to figure out what engages people and what doesn't? If it's "malicious false claims" then that's already a violation of defamation, there isn't any need for additional law on that front, but for anything else how can we decide in a way that can't be used the other direction?
That's always the rub and the core issue of free speech: there are no oracles. You have to imagine what your worst most hated enemy demagogue would do with the tools you propose to create, because they will have them. Nobody can be trusted with the power. It is hard though, and I won't completely dismiss the idea that the scale networking/storage/ML offers can create emergent effects that don't show up at a smaller level. The legal notion of tracking for example.
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0: though "amplify rumors over well-sourced reporting, demagoguery over reasoned debate" = the tabloids that exist right there at a large percentage of supermarket checkout aisles, remember nothing new under the sun, you might be surprised at some of the content of regular newspapers for that matter in the 1800s say.