The law of the land very explicitly says "Congress shall make no law restricting..." not "Rackspace shall shut down no website".
The spirit of the law, in the sense of what writers of the constitution intended is a lot more limited: not only did they specifically not want it applying to private property, they didn't even mean to apply it to states; several states had established churches. Fourteenth amendment incorporation is why is why the first amendment applies to state and local governments, as well as federal government. Some amendments e.g., second (The Right to Bear Arms) weren't incorporated until recently.
> but you are left with a society that is devoid of any free speech
You have your property, on which you can practice free speech. Find another managed host, colocate at a datacenter yourself or get a DSL line with a static IP. There's also public property: universities, libraries, public squares.
http://en.wikipedia.org/wiki/Pruneyard_Shopping_Center_v._Ro...