@Gotterdammerung I realise you're defending it, but thought you might find interesting that the "marketplace of ideas" trope has a chequered history. I'd found a piece years back by Jill Gordon, "John Stuart Mill and 'The Marketplace of Ideas'" which strongly corresponded to (and extended) my own thinking:
https://www.pdcnet.org/soctheorpract/content/soctheorpract_1997_0023_0002_0235_0250
More recently, David Runciman (podcast, sorry, and no transcript of which I'm aware) did a really good 'splainer in his "History of Bad Ideas" series on the Marketplace of Ideas as well:
https://www.ppfideas.com/episodes/the-history-of-bad-ideas%3A-the-marketplace-of-ideas
(Others may find that more useful than you will.)
If you'd like I can re-listen and synopsise the podcast for you.
Upshot though is that good ideas don't tend to emerge in a free-for-all marketplace. Laboratories, seminars, and non-motivated (dialectical, rather than sophistical / rhetorical) exchange. My argument is that "marketplace of ideas" was more about selling markets (many early advocates were also free-market advocates) than the metaphor vis-a-vis ideas themselves.
(If you go through especially Oliver Wendell Holmes's characterisation in Schenck v. US, one of the strong influences on him was Francis Wrigley Hirst, former editor of The Economist, itself created to promote free speech ideas as is made clear in its prospectus: https://web.archive.org/web/20180825113414/https://www.economist.com/unknown/1843/08/05/prospectus. The story's covered in The Great Dissent by Thomas Healy: https://www.kirkusreviews.com/book-reviews/thomas-healy/the-great-dissent/)
#MarketplaceOfIdeas #DavidRunciman #JohnStuartMill #ThomasHealy #FrancisWrigleyHirst #OliverWendellHolmes