The only reason why I believe what they said is that borking BGP will create the effect we saw yesterday, and why it took so long to bring it back up.
Bear in mind, with BGP down, there's no getting into the servers remotely to delete any nefarious information that needs to be scrubbed. Users would have to coordinate and go to each individual server, manually connect via serial cable, and then know where to find it on the server. The sheer volume of manpower required to pull off a stunt like this is extraordinary at best and outright ridiculous at worst.
As much as I want to knock FB down a peg, these are not the droids you're looking for.