Great question, which made me think about how they are more similar than I had originally thought. In both cases we're talking about carriers, quasi-utilities, network effects and (alas) real potential for abuse. But wouldn't this very similarity tend to
strengthen our intuitions about the need for community standards?
E.g. You are sitting on a bus, and a venerable person comes aboard and launches into paean to Bolshevism, urging the present company to rise up and seize the means of production. Certainly protected speech. You might find it entertaining. You might even feel a pang of nostalgia for a lost world and its simpler problems.
But after a few hours of this, would you really feel like a free speech abuse had happened if the bus driver asks our comrade to give it a rest; or, if he feels honor-bound to continue, would he please go do it on somebody else's bus?
But you asked how I thought they were different, and I do think they are very different, because human attention is limited in a different way than the number of busses, or ISPs are. If you can't fit one more person on a bus without kicking another one off, you can just buy more busses.
Human attention is not like that. No matter how many clones of twitter there are, I can't doom scroll for more than 24 hours a day. If some content is promoted on my feed, that means other content is inevitably excluded from my feed. And isn't this really what people are unhappy about? Not just that their views are not stored in some database somewhere. No, they want people to pay attention to what they are saying.
Can that problem be solved by additional regulations? I really don't think so. No matter what regulations we put on carriers, there will be media winners and media losers. And the losers will always feel like the system is systematically excluding them. And no wonder they feel that way--they are right. They can even go beyond vague complaints of corporate collusion and point to specific line items community standards, or--if we do adopt regulations--to specific regulations which are having the effect of suppressing their speech, perhaps even unconstitutionally suppressing their speech. But the conundrum is that this would be true for any set of regulations. The regulations can change who gets attention and who gets ignored. And they can make a bus ride or a social network more pleasant or less pleasant. But I have a hard time seeing how it can actually solve the problem of people being ignored.