I agree with you insofar as Mill's free market of ideas is the best remedy against bigotry and extremism, but you have the wrong idea about how to achieve that -- unregulated laissez-faire "freedom" on the web does not result in actual free discourse. On the contrary, that's just a recipe for a web overrun by all manner of adware, malware, spyware, propagation of unconscious self-censorship by means of universal targeted and mass surveillance, and straight-up disinformation ops and public opinion manipulation from hostile actors. How are you going to have sincere exchanges of ideas at scale over all that noise?

Similarly, there’s not that big difference on “policing” - the social media companies enforce very basic terms of service but most people use web hosts with relatively similar terms. The major difference is the discovery mechanism (and the fact checking applied to certain politicians’ accounts which aren’t banned on public interest grounds) which is closer to how search engines avoid sending links to certain sites with bad reputations. A lot of what Twitter/Facebook block will also be dropped by Google or many free web hosts. You can definitely get away with more but I don’t see much reason to believe that it’s a major difference rather than minor variations depending on which companies and content you’re talking about.