Hitler rages against and wishes to destroy "Jewish parasites." The parasite, in actuality, is Germany,  the "immortal object" with which Hitler identifies. The parasite is Hitler's own fantasy of immortality, the German nation, to which he has sacrificed his existence.

But Hitler cannot acknowledge that Germany is the parasitical object that torments him--because this would mean abandoning Germany, the object that torments him, his fantasy of immortality.

So Hitler projects the idea of the parasite onto the "eternal Jew." It is not his devotion to Germany that is draining his life; depriving him of a human existence. Rather, it is the Jewish parasite that is draining--depriving him--of his own existence.

But the Jew, in actuality, is a projection of the parasite within Hitler (Germany), which Hitler refuses to abandon. The parasite is Hitler's own fantasy of eternal existence, which torments him but from which he is unable to separate. 

Given his ambivalence, Hitler would have to wage endless war against the parasite, to kill Jews forever--in order to liberate himself from the object that torments him. 

Hitler's struggle (Mein Kampf) could end only when he killed the source of the parasite, himself, the Jew within his own mind and body, Germany.