For all the crap that is said in the Chinese media, I always wonder if they have at least 2 neurons to think what would happen if the US starts using their own media machine to play the same kind of game (Oh, the irony!).
I'm sure it can be very unpleasant if you have the US media machine turning against you in any kind of story.
From what I can understand, the Seventh Fleet is in the area. So my guess is that the "threats" are aimed at the Fleet, especially since the Navy sent a P-8A Poseidon to take better photos of the infrastructures built by the Chinese on the island on a regular basis. So far, that's all: a plane taking photos of a construction being built in an illegal zone. What is it to get pissed about? Either way, China's presence is already an ecological threat with the way they are destroying coral reefs through construction out there.