I would like to link to a handful of modern-day Smedley Butler types (though none afaik has been invited to serve as figurehead for a coup!) -- this is just a few off top of head, but it would be an interesting project to assemble an extensive Whistleblowers' Bookshelf:

John Perkins:  Confessions of an Economic Hit Man

Joseph Stiglitz, Globalization and its Discontents

Philip Agee, On Company Business, CIA Diary

My buddy Stan Goff, Hideous Dream  a memoir of the 2nd (or was it 3rd?) US occupation of Haiti

The VAW collective who produced the Winter Soldier Reports (see also the documentary Sir No Sir! for more details on the US troops' and veterans' anti-war movement).

There is a small but honourable society of former mercenaries, thugs, high priests and enforcers for Empire who repented, recanted, and decided to blow the whistle on the mafia they used to work for.  Their former associates doubtless regard them as stool pigeons, squealers, and traitors;  the rest of us, I think, should be grateful for a view, however limited,  of the dirty laundry of our overlords...

The difference between theory and practise in practise ...