If it's free speech, and they are carrying significant levels of public traffic, then "No", they shouldn't be allowed to censor content.
If they don't like that requirement, they should find another line of work. I don't care who owns the telephone poles. By G@d they'll carry it all, or they won't carry any of it!
I’m beginning to think that your 1m user test is a fiction and that you just want everyone to be able to post their their random thoughts on anyone else’s platform - for free.
Only if they carry other traffic for free. If they charge other people, they can charge everyone. What they cannot be allowed to do is get huge numbers of communication traffic, and then control what that traffic is.
Now you're back to saying Jim can't ban people.
You try to hide behind "huge numbers" but that's just a convenient dodge because your basic premise is so preposterous.
In the authoritarian world you advocate government will define 'huge' and you won't have any say - or property rights.