I hope this gives some pause for people who advocate the XKCD line on free speech[0]. While not every platform should be required to host every kind of content, when a platform becomes sufficiently dominant, its ability to censor content becomes a free speech issue.
While you bring up a valid issue (per e.g. [1]), it's not clear to me what you're trying to say about it. Even less clear to me is how any sort of coherent legal regime would be imposed on something like Internet.org, which presumably has access to sufficient resources to carve up its legal entities into the tastiest possible slices (such that e.g. the local entities only run the base stations while content approval decisions are ostensibly made by a mailbox in Panama or whatever).
I wasn't saying that Facebook should be regulated like shopping malls. I was saying that people who say that private censorship is not problematic, do not have an answer for things like internet.org. Facebook are legally free to set up programs like this, but people are also right to criticize Facebook for setting up a system that takes away from the freedom of the open internet. The shallow analysis of the XKCD comic ignores these issues, yet I often see that comic posted when people complain about left wing censorship online.
A daily comic isn't the medium that one usually chooses for subtlety or depth. A lot of people complaining about "left-wing censorship" (or "right-wing censorship", for that matter) are in serious need of a clue-by-four and wouldn't bother reading a deep analysis if it were given to them.
But people complaining about "corporate censorship" are smart well informed people? How is internet.org controlling what website people get to see different from, for example, YouTube controlling which videos people get to see? And how are the whims of whoever will control or influence internet.org different from the (mostly left wing) groups that (sometimes successfully) pressure companies to remove material from their websites.
[0] https://xkcd.com/1357/