The reason why the mainstream media contribute to it is that those media are owned by the same powers that set the agenda of US (foreign) policies.
Media ownership is not exactly a secret and speaks for itself (see www.takebackthemedia.com > who owns the media)
Official doctrine speaks less for itself, and requires evidence - in this case declassified State Department documents from 1948.
====
From a debate between Noam Chomsky and Richard Perle at The Ohio State University in 1988
http://www.radio4all.net/proginfo.php?id=8409"One learns a lot from looking at the documentary record, and one learns a lot from the fact that certain people don't want you to look at it." - Noam Chomsky
"Official doctrine is quite inconsistent with the historical and documentary record. Official doctrine conforms to the pattern of evolving events (US support of RW dictators and vilification of socialist governments), and is entirely inconsistent with widely proclaimed doctrine." - Noam Chomsky
Quotes from declassified State Department documents:
On the 3rd World:
"...a source of raw material and markets for the industrialist capitalist powers, to be exploited for their reconstruction"...
On Latin America:
"Prime concern is the protection of our raw materials. We have 50% of the worlds wealth but only 6% of its population, we must maintain this disparity to the extent possible, by force if necessary,
putting aside vague and idealistic slogans such as human rights, raising of living standards, democratization, preferring police states if needed over democracies that might be to liberal and to indulgent to
communists, the latter has lost any substantial meaning in US political rhetoric,
referring simply to anyone who stands in our way."
"The primary threat to the US in Latin America is the trend towards nationalistic regimes that respond to popular demand for improvement in low living standards and production for domestic needs. That's not acceptable because the US is committed to encouraging a climate inductive to private investment, in particular guaranties for opportunity to earn and in the case of foreign capital to repatriate a reasonable return."
"We must therefore oppose what is regularly called ultra nationalism in secret documents, that means efforts to pursue domestic needs. We must foster exports or (...) production in the interests of US investors. It is recognized such programs have very little appeal to the Latin American public. So the conclusion is that we must therefore gain control over the military which can in turn control domestic opposition and
overthrow civilian governments if necessary."
====
"There is a declassified State Department paper from 1948 that outlines what the US intended to do with various regions of the world after World War II. The US decided to take the Middle East and Asia. When it came to Africa, the document essentially says that we're not so interested in Africa, so we'll give it to the Europeans to "exploit"-that's the word used-for their reconstruction." - Chomsky
http://www.madre.org/articles/chomsky-0801.html====
I. Fundamental Principles: Straight Power Concepts
The fundamental aims of Western foreign policy under American leadership, were stated in a now declassified top-secret planning report produced by the US State Department’s policy planning staff, headed at the time (February 1948) by the ‘liberal’ George Kennan: "We have about 50 per cent of the world’s wealth, but only 6.3 per cent of its population... In this situation, we cannot fail to be the object of envy and resentment. Our real task in the coming period is to devise a pattern of relationships which will permit us to maintain this position of disparity without positive detriment to our national security. To do so we will have to dispense with all sentimentality and day-dreaming; and our attention will have to be concentrated everywhere on our immediate national objectives a pattern of relationships which will permit us to maintain’ the ‘position of disparity’ between the West and the rest of the world. We need not deceive ourselves that we can afford the luxury of altruism and world-benefaction...
We should cease to talk about vague and... unreal objectives such as human rights, the raising of living standards, and democratization. The day is not far off when we will have to deal in straight power concepts. The less we are then hampered by idealistic slogans, the better.’
http://www.transcend.org/t_database/articles.php?ida=78