Agreed. We generally allow companies to refuse service for nearly any reason, and in most cases this is a good policy. However, there are exceptions to that rule. One extreme are utilities which as both monopolies and essential services are required to do business with nearly any paying customer, and have strict rules processes about shutting of service for lack of payment. Residential rentals are another example. They don't hold a monopoly, but are an essential service, and as such they can generally choose who to do business with (although not quite as freely as your average business), but have strict legal processes they have to follow regarding evictions.

I think there are online business who are essential enough that some consumer protections are applicable. Very few reach the level of monopoly that utilities have in my mind, and even those it isn't clear to me that they are "natural" monopoly like utilities, and as such other antitrust approaches may be more beneficial.

However, I think there are a number of competitive, yet essential services online that deserve a legal protections regarding service termination. Identity providers absolutely fall in that category IMO - it is unacceptable for example for Facebook to lock your account in a manner that prevents you from not only using their services but every other third-party service which you authenticate using "Logon with Facebook". I think email is another that rises to this level. At a minimum email providers should be required to forward mail for a fixed period of time after choosing to stop doing business with a customer.