Saul Friedländer mentions in his Pulitzer-awarded The Years of Extermination that during his Sportpalast speech, Goebbels at one point makes a telling slip of the tongue:
Germany in any case has no intention of bowing to this threat, but means to counter it in time and if necessary with the most complete and radical extermi—[correcting himself]—elimination” [Ausrott—Ausschaltung].
I've been wanting to hear this part myself, but haven't found any audio that contains this part. The audio linked on the German wiki, for instance, completely cut this paragraph (at about 21:30). There's no mention of the audio's source though and if it was a Nazi recording, they might as well have censored it.
Still, according to the full text at 1000dokumente.de (a site of the Bavarian State Library) Goebbels never says "Ausrott-Ausschaltung", but "Gegenmaßnahmen" (countermeasures):
Deutschland jedenfalls hat nicht die Absicht, sich dieser Bedrohung zu beugen, sondern vielmehr die, ihr rechtzeitig und wenn nötig mit den radikalsten Gegenmaßnahmen entgegenzutreten.
Can somebody please explain?
As far as I can tell, the 1000dokumente text is based on the "official" transcription, there are several grammatical errors from the original speech edited. Unfortunately, the source, DRA-Nr. 2600052, which means it's in the Deutsches Radio Archiv, can not be accessed from the internet.
However. Here is a suspicious youtube link.
In which Goebbels says exactly that. Well, he says "Ausr- schaltung", which is nearly as good. Note that the recording is heavily edited and no source given.