My data supports what you are saying here.

Here is an English translation of his book.

https://ia601304.us.archive.org/26/items/practical-idealism-english-ver-1-2/Practical_Idealism_English_Ver_1_2.pdf

Taking into account that different translations will rarely be identical and that an translation itself may use varied wording, etc, to express the original, one can still run a search for a few things and find NOTHING along the lines of this so-called 'Quote':

eg

Negro, negroes, negros, black - all of these ZERO hits.

"Mixed" - 5 hits in the original text, none of which bear ANY resemblance to the so-called 'quote'

Mongrel - zero hits

The translator makes a few comments re: the 'Kalergi plan'

This English translation of Praktischer Idealismus is the product of several months of dedicated volunteer, non-profit research and translation work to ensure as clear and complete a translation as possible. The original German edition is no longer available in stores and, as such, the document had to be sourced from a digital scan of the 1925 edition. Poorly translated and truncated excerpts from this work have been widely circulated across the Internet to advance the idea of a Kalergi Plan, a theory which purports a concerted effort by Coudenhove-Kalergi to bring about the destruction of European cultures and peoples. As the translator of this work, I remain intentionally neutral on the matter. Rather, it is my desire to present the book in a complete and well-translated format, containing footnotes to expand on the text and to provide useful historical context. I expect that many readers will have found this translation precisely because of their encounters with the Kalergi Plan narrative. I ask that everyone who reads this work go into it with a clear and open mind.

The translator also makes a note on Chapter 4 'Inbreeding - interbreeding'

Translators note: This chapter has been the primary driver of the so-called “Kalergi Plan,” a theory that purports a conspiracy by Coudenhove-Kalergi to flood Europe with non-European peoples in order to destroy European civilisation. While CoudenhoveKalergi does discuss the mixing of different peoples, including marriage, no evidence has yet been shown to conclude that such a plan ever existed. Excerpts from this chapter, typically with limited context, have advanced the notion, but a proper reading in the context of Coudenhove-Kalergi’s time should dissuade readers of this idea.

Now, the really interesting question is, who would feel it valuable or necessary to present disinformation in the way it is presented here? Who would create a false quote, attribute it to Kalergi, and then promote it to the public? And, why?

Because, honest people who value truth (and freedom that derives from truth) do not create this sort of disinformation.

I'm not saying Kalergi's ideas were good. I'm asking, why would someone want to create fake quotes?

My personal opinion: the old eternal dynamic of divide and conquer is at play. We are offered two sides that present themselves as opposing or different: the radical anti-semite, who hates 'Jews', and the so-called Jews and their minions; two sides of the same coin.

The entire "The Jews are Evil" narrative stream provides energy to, and gives a reason for existence to, the Anti-defamation league, who then provide further evidence that 'the Jews Are Evil". They feed off each other.

We see that dynamic in a slightly milder form in the Democrat Vs Republican framework of the modern era. In reality, they are (have become) the uniparty. Bush = evil, Obama = good vs Obama = evil, Bush = good. The truth? Both Bush and Obama are creations and instruments of the same corrupted clique behind the whole mess.

The real truth is that both sides have the same purpose and goal.

If anyone is interested in pursuing this idea further, I can recommend a really excellent (I think) line of research in The Book of Trump, Chapter 25: The Uniparty [of False Decorum]

https://rumble.com/v6ws6iy-the-book-of-trump-chapter-25.html

Ghost of Based Patrick Henry reveals, via his research, how the modern 'Republican Party' aka the Neo-Con movement, traces its roots to Trotsky and Trotsky disciples.

It's a mind blower. He raises the matter of the collaboration between the Zionist Jewish movement and the German Nazi's to destroy European Jewry so that they would HAVE to be transferred to ... bingo, a new nation of Israel.

How about that? Jews actively seeking to destroy European and relatively secular Jewish communities (Jews) and peoples in order to realize the Zionist ideal.

So who is evil? Is it 'the Jews'? Because they are all the same? Or is it the Zionist clique that seeks destruction in order to accomplish their goal? It is Germans who were evil, or was it the Nazi regime that was evil?

The answer should be obvious, but only becomes truly obvious when you examine the facts, and step away from the reacitonary, emotionally triggered narratives that want to paint X <generalized group> as demons in order to control how you think about <them>.