The point is that when a social network is large enough to become significant in the way people communicate, the way thought evolves in society, etc, it becomes a societal issue that the owners of that network can (and, as you keep pointing out, are completely within their rights to) arbitrarily restrict what people can say.
In case it's not clear, I don't claim that Twitter doesn't have the legal right to moderate their platform. I claim that it is a problem for society that more and more of our public discourse happens on platforms with this type of arbitrary moderation.
You don't have to use twitter, Facebook, or any other platform. If you are dissatisfied with the rules then make your own.
Just because something has become a major player in communication, doesn't meant these companies should be obligated to turn a blind eye to content that they find disagreeable.
Also, I have yet to see a case where anyone has been "arbitrarily" restricted. They conform to the rules as clearly stated on their website. If anything I have seen that they are not doing as well as I wish they were at enforcing their rules. But it largely makes sense that the bigger you are the more scrutiny you will have on your tweets.
It isn't like just because you have an account on twitter you can't have an account on some alternative.
I've tried twice to make it clear that I'm talking about the wider societal issue of the growing importance of these platforms in public discourse combined with their moderation policies (and the arbitrariness of those policies — since they can change at any time without notice).
Since each of your replies ignores this and focuses on individual issues — unrelated to my comment and uninteresting to me — like which platform(s) a person chooses to use, whether Twitter has the right to moderate, or whether they have historically used their arbitrary moderation power in a way that you find acceptable, I'm going to disengage from this thread at this point since I don't think we can enlighten each other in any meaningful way.
In case it's not clear, I don't claim that Twitter doesn't have the legal right to moderate their platform. I claim that it is a problem for society that more and more of our public discourse happens on platforms with this type of arbitrary moderation.