This reminded me of one of Friedrich's most famous aphorisms. It is from Beyond Good and Evil: "146. He who fights with monsters should be careful lest he thereby become a monster. And if thou gaze long into an abyss, the abyss will also gaze into thee." Especially this second part, the second sentence of this aphorism can be described in psychoanalytic terms, in terms of "projection" or "projective identification."