When the DHS comes in and shuts the board down because we're all a bunch of terrorists the 1st claim can be made. Until then it is private citizens (and the companies/property they control) acting as they see fit.
Monky has it right, FB had to respond to a copyright infringement. FB may have enjoyed doing so or maybe not. It was generating lots of views and publicity so FB was probably making more money off our satire pages than they will off the real one.