>Saying that Facebook, Twitter, Paypal, et. al face any actual injury or diminution in service as a result of hosting pernicious speech is absurd,
It isn't absurd because an example of such an injury happened last year at YouTube with the "adpocalypse" demonetization debacle.[1]
- Various uploaders put objectionable content on Youtube. Google/Youtube doesn't censor or filter it out.
- Viewers complain loudly about it and threaten to boycott the major advertisers that ran ads against it (e.g. Proctor & Gamble, etc)
- P&G and other advertisers abandon Youtube and Google loses millions[2]. The innocent Youtube channel creators who created mainstream content also lost AdSense reveneue because they got caught up in the stricter content crackdown.
- Some advertisers finally return. E.g. P&G after one year.[3]
Facebook and Twitter can't realistically be an "any and all free speech including hate speech" platform because they are beholden to advertisers. They have the same platform funding dependence as Youtube/Google.
Those social media websites are not in the lower layer of the TCPIP stack such as "common carriers" ISPs like Comcast and Verizon. Those "dumb pipes" telecom businesses are less sensitive to whether a TCPIP packet is routing bytes for hate speech vs pictures of cats.
[1] https://en.wikipedia.org/wiki/Censorship_by_Google#Advertise...
[2] https://www.google.com/search?q=biggest+advertisers+abandon+...
[3] https://www.tubefilter.com/2018/04/20/pg-resumes-youtube-spe...