I don't get why people feel the need for Facebook or Twitter need to host those items on their own servers?
Do people not realize that these are private companies with editorial discretion?
Having said that, their right to exercise editorial controls on their platforms does not mean they are somehow above criticism when they elect to do so in stupid ways. As the original comment in this thread suggested their moves in regard to speech are short-sighted and detrimental to the overall health of society, especially given the pervasiveness of use of these platforms. Still, I can recognize their right, and call them out on their foolishness, at the same time. I only cross the line when I demand force to be used against them (meaning a law written to force their hands); then I would be in the wrong. They don't have a responsibility to further discourse and I don't have a responsibility to hold my tongue when they fail in this regard.
I would argue that anyone who takes it upon themselves to become the central hub for most discourse (or to organize the world's information) has an implied responsibility to act as a good steward of the empire they seek to control. We have no obligation as members of the public to accept whatever controls a land-grabbing (I use this term here non-judgmentally) empire builder wishes to impose; they sought to turn us into members of their empires, so we should at least have the right to demand they behave equitably, and perhaps even beneficently.
When we use a Facebook or a Twitter, we (the public) accept the product they offer. True enough, if we find out we don't like the deal we can threaten to walk away if there is no change. But these companies don't have a responsibility, implied or otherwise, to better us, cater to any of us, or fulfill someone's vision of social good. It would be nice if they delivered on these things (of course my vision of what that means) but it is not their responsibility to do so. If I don't like that with sufficient intensity, my one valid recourse is stop using their services.
The source of the implied responsibility of beneficence is the fact that without assuming such a responsibility the acts of a corporate empire are likely to be destructive to the long term interests of the society. By (for example) controlling the social network, they leave members of the society with limited choice not to participate, and thus the implied responsibility of beneficence in exchange for that removal of choice.
The difference is that nobody is asking for these companies to be banned or to cease operations. They are free to do what they want and we are free to ask what we want.
So, in order to prevent that situation, we allow one company a monopoly on the market. In exchange, that company is forced to follow common carrier rules, such as not interfering with speech.
We all agree to use the same company for infrastructure, just like we all agree to use the same couple of companies for social media. It's just when the social media companies do things that are bad people pop up and say "they are private companies in a free market they can do whatever they want" because these companies are new and cable companies are old.
The issue is that its hard to get the message out with a few brands dominating the internets. How will one get the message out about a website if she or he couldn't blog about it on a platform like Twitter or Facebook?
p.s. I might be reading you wrong here