Records of speeches are incomplete. For example, I have a recording of JFK that doesn't seem to appear in the official audio collection of "all" his speeches. JFK came to Norfolk, VA and made a short speech. It was released on an LP at the time, and I have a copy in my collection. I think it was the one on 11-4-1960, just before the election.

So it may be that not all Kissinger speeches are recorded, or at least not available to the public, if they need to stay hidden. Kissinger may or may not have said the attributed quote, but I wouldn't put it past him, as he was totally in favor of population control.

There is a YouTube video of someone holding a clipping of the quote, whether real or not, same as the image in the tweet: https://www.youtube.com/watch?v=vRyPk7gHARQ

There is an American Eugenics Society. Here is a link to a membership booklet, but there is no Kissinger listed: https://archive.org/download/AMERICANEUGENICSSOCIETYMEMBERS/AMERICAN%20EUGENICS%20SOCIETY%20MEMBERS.pdf

Here is a site that contains the quote plus another similar one from Kissinger, as well as some related info, all from 2016, before the "plandemic": https://www.theeuroprobe.org/2016-082-authoritarian-globalism-and-libertarian-populism/

Here is a document from Kissinger in 1974: https://www.scribd.com/document/6474391/Henry-Kissinger-Population-Control-Document

Here is a report on that document: https://lifeissues.net/writers/clo/Kissinger_Report_2004.pdf

I used Yandex.com instead of Google for my searching.

If Kissinger really said this, it would have been carefully scrubbed.