Whether covert action is "the essence" of U.S. foreign policy is debatable. It is rotten in that it undermines U.S. interests from within. It certainly did so in Mexico during Win Scott's tenure as station chief.In return, Mexican officials would look the other way as the CIA used Mexico as a base of operations to achieve regime change in Cuba entailing the ouster or assassination of Cuban president Fidel Castro.
Here, in a nutshell, is the essence — and the rot — of U.S. foreign policy: Make sure that “our” people are in public office in countries all around the world, either through bribery, influence, assassination, coups, military training, military aid, or foreign aid. Do favors for them. Give them money. Do whatever is necessary to ensure that such officials will respond positively when the U.S. Empire needs a favor.
Your can read Hornberger's entire post here.