A privately-held telecom provider (i.e. utility) disagrees with my political views. As a result my internet service is terminated.
Let's agree the definition of a public utility is "Furnishes an everyday necessity to the public at large".
Has the provider restricted my First Amendment right?
At what point (if ever) would you consider Facebook/LinkedIn/Twitter public utilities?
Is Twitter or any other application layer non-government service on the internet a utility? No.
So is this what happened? No.
They didn't ban him for his political views, nor are they a utility.
No, they banned him for soliciting harassment, not for the views which motivated the solicitation of the harassment.
I believe you are referring to twitter being used to silence a dissenting opinion when you said "that policy", in reference to Nero. I actually think it's the other way, the bullying sent toward the SNL actresses' way, the sexist and homophobic comments, those were actually meant to silence a dissenting view, someone those people did not like.
Stopping bullying is a good thing. No good comes from bullying someone you don't like.
On the internet you can choose whatever service you like.
Or, lets go for something simpler: Spam. You're using the telcom provider to send out spam. They cut you off for it.