George Plimpton was raised and lived in the heart of America's establishment. He was friends with CIA types his entire life.
Throw away the notion that Plimpton (and by extension the Paris Review) had no ideology. Plimpton was the personification of classic American liberalism. He believed in an outward-looking foreign policy in politics and culture. He implicitly believed in Owen Wister's phrase that "true aristocracy is true democracy"; that the cream always rises to the top; counting himself of course among that number.
It's an ideology compatible and consonant with U.S. Imperialism. (The preferred word is "globalism.") George was the creation, like so many other Americans of his time, of Franklin Roosevelt, who might be called the first American Imperialist; the first President to envision global American Empire, who worked to set that empire in motion.
George Plimpton didn't need to conspicuously advocate this vision, this ideology, in Paris Review's pages. It's a vision which overwhelmingly predominates in American political and intellectual circles, and was subliminally present in everything PR's editors did and said. One can't be considered an "intellectual" in America today without believing the vision: a dominant ideology far more strongly rooted in our society than Communism ever was in the Soviet Union.
Those who disagree with the vision exist on the margins.
Paris Review's office in Paris, and its very title, were an expression of Empire. They said, "Here's our American outpost."
No policy was explicitly advocated in PR's pages. How do you advocate something which is present all around you; which exists in your own society unchallenged? (Anyway, to do so would've been gauche.) Their need was instead to present art free from politics, from polemics, from social conscience; which stressed as role model to the world soon to be conquered a vision of American success and affluence. Paris Review's most celebrated writers fit that role well.