“It is just like man's vanity and impertinence to call an animal dumb because it is dumb to his dull perceptions.”

On his blacklisting in 1953
The Guardian interview (2002)
Context: A man comes from New York. He says, "These petitions, your name is on all of them: anti-poll tax, anti-lynching, friendship with the Soviet Union.... don't you know the communists were behind them?" And he said, "Look, you can get out of this pretty easy. All you got to do is say the communists duped you. You were dumb. You didn't mean it." I said, "But I did mean it!" To this day people say, "Oh, Studs, you were so heroic." Heroic? I was scared shitless! But my ego was at stake. My vanity. "Whaddya mean, I'm dumb?"

Source: Selected Essays, 1778-1830

Kissinger has denied saying it.
The only evidence that Kissinger ever said this was a claim in the book, The Final Days, by Bob Woodward and Carl Bernstein, in chapter 14 (p.194 in the 1995 paperback edition). Woodward & Bernstein claimed that one of Kissinger's political foes, Alexander Haig, had told someone unnamed, that he (Haig) had heard Kissinger say it. That's triple hearsay, made even weaker by the fact that one of the parties is anonymous. Kissinger has denied ever saying it, and it was never substantiated by Haig, nor by anyone of known identity who claimed to have heard it. As Kirkus Reviews noted about the whole book, "none of it is substantiated in any assessable way."
In fact, the quote is not even very plausible, on its face. Kissinger served with distinction in the U.S. Army during WWII, and was awarded the Bronze Star. He has always been very respectful of other servicemen and their sacrifices. For him to have said such a thing would have been wildly out of character. In fact, the awkward phrasing doesn't even sound like Kissinger, whose English prose is consistently measured and careful, despite his heavy accent, even when he speaks extemporaneously.
Misattributed

Dumb All Over.
You Are What You Is (1981)

Mat Rona Ramjani Chacha (Poetry Collection), Kavysangam Books, 1999.

Similar terminology is used about males as a defamation of character, or more broadly only about pressed males males: stud, wold, cat, stag, jack - and then it is used much more rarely, and often with a specifically sexual connotation.

Chapter Four
The Dialectic of Sex (1970)

Southern Accents
Lyrics, Southern Accents (1985)

Woodward and Bernstein. The Final Days, chapter 14 (1976)

Source: Dreams of a Dark Warrior