That said, if you want to read things into what I said and actually have this conversation, does my hosting provider have to host my website? Does their ISP have to not cut them off if they do? Under a narrow reading of "free speech" as "stuff protected by the First Amendment", obviously not (unless the ISP is run by a government entity, of course). Under a reading of "free speech" as "the ability of society to not have entities with overwhelming power (governments, but not only them) suppress speech they don't like", the situation becomes more complicated.
And I would argue that a narrow legalistic focus on the First Amendment is not the right way to approach the problem. The First Amendment is a means to an end, not an end to itself. For an 18th century analogy, if a private company has the power to go around destroying all printing presses that don't belong to them and refuses to print views it disagrees with, that is just as much a problem for free speech as if the government were doing it. This was just not a realistic scenario in 18th century North America (unlike, say, contemporaneous India), so wasn't a big concern for the framers of the First Amendment.
Is this a scenario we have to worry about now? It's not clear to me that it's an imminent problem right now, but I can easily see it becoming one in the next 10-15 years. Might be worth thinking about norms (and laws, as needed) now so we're not playing catch-up when it does.
None of that has anything to do with the factually inaccurate claim about the narrow constitutional right that was made in https://news.ycombinator.com/item?id=25673573