I don’t disagree with any of that. My point is simply that I believe it’s fully within their right to do so like it or not.
I would say yes, although if they make that decision based on subjective criteria, they are providing a publishing function, and can be sued by individuals for what is written on twitter.
And in fact, if “banning” is described based on a violation of rules, and the rules were not in fact violated, that could be libel — a person who is not recognized as a public figure could sue saying that Twitter’s banishment for “offensive posts” which were not in fact offensive is libelous and damaging to a person’s reputation.