Toward the beginning of his remarks Gilbert, referencing his 1999 book Must Global Politics Constrain Democracy?, comments briefly and in passing on George Kennan:
In most foreign policy discussion and international relations as an academic field, realist theories - both official ones used in making/apologizing for American foreign policy and more sophisticated versions employed in the critical study of American errors and crimes, even systematic ones - abstain from the outset from looking at the consequences [of U.S. foreign policy] for democracy at home....
For instance, the leading post-World War II realist, George Kennan in American Diplomacy, pits sober, professional diplomacy against democratic crusades like Woodrow Wilson's in World War I.... But in the 1984 edition, responding to the disastrous American aggression in Vietnam, Kennan noticed the war complex, "our military-industrial addiction." He shifted to a more democratic, common-good oriented view without naming the shift.Kennan opposed the Vietnam War from the start mainly on pragmatic grounds (he testified against it in congressional hearings in 1966), and Vietnam probably did influence his thinking. There are tensions in Kennan's views deriving partly from the way in which moral considerations are often kept unacknowledged or beneath the surface, with the biggest exception to this being his increasingly passionate writings, starting in the 1980s, about nuclear weapons. But I think Kennan remained ambivalent, at best, about democracy until the end of his life. These tensions (or contradictions) run through much of his career, complicating the idea of an un-named shift "to a more democratic, common-good oriented view." Still, it is interesting that some of the language in American Diplomacy, originally published in 1951, changed in the 1984 edition.
P.s. A minor point: "One of the leading post-WWII realists" would have been better than "the leading," since Morgenthau, Niebuhr, and Kennan are usually given roughly equal billing as the key figures of post-1945 American Realism, with Arnold Wolfers, John Herz, and some others not far behind. (Generationally speaking, Waltz and Kissinger come after this group.)
Added later: It's possible to put a somewhat more uncomfortable (for lack of a better word) gloss on Kennan's position on Vietnam, which would note that, in addition to his (correct) judgment that Vietnam was not a vital U.S. interest, he just didn't care much about the Third World (as it was then called) and didn't think non-Europeans (or non-descendants of Europeans) had much capacity for self-government. But going into that would require another post.
[To find previous mentions of Kennan on this blog, type "Kennan" into the search box in the upper-left corner.]