The US government has an immense amount of evidence on SIPRnet of war crimes, crimes against humanity, and other heinous acts committed by the members of the 5-eyes War Coalition.
It is sitting on this evidence, and not allowing it to be viewed by the American public, because the degree of criminal behaviour would radically alter the military power networks of American society. Thus, "national security", and everything is kept secret, and all military resources are used to ensure those secrets are kept.
This is a heinous situation for American citizens to be in.
Indeed, the rioting and burning of America, were the average American come to a real understanding of what, say, was done to Mosul or Raqqa, in their name .. would be true awe inspiring. American's are happily angry, after all.
So, this is why we have a situation where the general American public are kept utterly ignorant about their wars, and their war victims especially, and instead are trained to buy in to America's biggest industrial society.
This "message to journalists" is the tip of a cold, icy berg of dark, dark secrets. Until the American public flip, and see the power of the leaks themselves, first-hand perhaps, in a reconstruction of their social order, then there will always be more need for leaks.
Leaks haven't actually killed anyone - in fact, the leaks have saved millions of lives.
The bombs America and her allies drops on their enemies, every twenty minutes, however: do kill people.
The leaks will continue.
(Note: this comment submitted in a humble effort to provide a counter-weight to the raging torrent of nationalist pride that allows 5-eyes citizens to justify their nations war crimes. It is a conversation that must be had, downvotes be damned..)