>it is possible to start your own ISP

And where do you suppose ISPs get internet from?

From a blended mixture of peers and transit providers, such that a termination of service from any one peer does not take the network offline.

We have already supposed that all hosting providers have terminated you, and all DNS providers have terminated you, why shouldn't all ISPs terminate you?

Well great! People with enough time, money, and know-how to start their own ISP don't have to worry about Facebook and Google censoring them.

Not looking to good for the rest of us, though.

Or, those with the time, money, and know-how can do these things today, so that others that they are sympathetic to will have more options available to them when they are shut off tomorrow.

And the result is Gab. A site full of people who were banned from Twitter. About half of the "popular" tab is ranting about how the Holocaust never happened, diversity is a weakness, and (((they're))) going to kill all the white people soon. The other half is about how awful Twitter is to ban people. The now-defunct Talk.Tor, and 4chan's /pol/, are the same way.

Most of the users that Twitter and Facebook deletes are actually people (or spambots, but even Gab blocks those) who ought to be deleted, so any service that's primarily filled with expats from them gets filled with slightly-oblique calls to violence and general quackery.

So when a poor user who isn't a skinhead gets banned because someone who happens to have the admin bit has a personal beef with them, they're supposed to switch to Gab? That's not an okay alternative.

I'd offer Mastodon as a healthier example of somewhere Twitter/Facebook refugees can turn. I'm sure there are some federated instances that harbor the type of toxic behavior you describe, but on a well-moderated instance, they'll get depeered pretty quickly. And there are lots of instances to choose from, so a bad admin just means you need to find a new instance -- you're not cut off from the entire platform.