To what degree do we have evidence that politicians actually feared the the spread of communism/wanted to spread democracy for ideological purposes compare indications of to economic motivations?
The problem is that you're assuming motivations can be and are exclusive of each other. Economic motivations and considerations do not obviate ideological or political or strategic motivations and goals.
I can recommend a great book on the topic: The Brothers, by Stephen Kinzer. A biography of the Dulles brothers, who concurrently served as the sec. of state and the head of the CIA, it explains their motivations -- many of them economic -- behind US policy toward Guatemala, Cuba, Vietnam, the Congo etc.