If none of this information was really a leak of actual classified information, then there would be no reason to block the Guardian. Blocking The Guardian implicitly confirms that some of the information that they are released really is classified information.
Not really. The Guardian claims to be sitting on a pile of additional information that it hasen't yet released. So blocking the site could be a preemptive measure to deal with potentially classified information potentially being published at any given time in the future.
