Your right, this legal "hack" would probably be frowned upon by a judge, but it does demonstrate how silly it is that the literal carrier is not the one considered the "common carrier".
It would be illegal for Facebook to arbitrarily prevent someone from accessing Facebook, and legal for Comcast to arbitrarily prevent someone from accessing Facebook. And back to my original proposal, if Facebook and Comcast came to some sort of deal, perhaps Comcast could block unwanted user on behalf of Facebook.