Comment by kelnos

I think there should be two tests:

1) Does the reason for terminating a customer violate law that protects certain classes of people/orgs? If so, you can't do it.

Obviously there are jurisdictional concerns here, but let's assume we can navigate them successfully, at least most of the time, without a messy court battle.

2) For any content, regardless of #1, does the customer have other choices besides you? If not, you can't do it.

For the second point, I think that should be there to protect from a company arbitrarily imposing its values. My feeling is that if there's enough healthy competition (I won't define what "enough" is because I don't know, but hope that it could be definable), someone will host your content. And if no one wants to, that should be a pretty clear signal that you're so unbelievably far away from what the vast majority (or even the near unanimity) would consider acceptable that you really will want to rethink some things.

If you are the only option, then likely you are a legally-regulated monopoly anyway and have some rules around needing to offer service blindly (rules imposed in exchange for that monopoly status).