Symbolism, Imagery, Allegory
The Interrogator has great admiration for his new-fangled torture machine, the "autopilot," because of its seemingly civilized method of destroying someone.
They said that about the guillotine, too, folks.
There's no visible brutality involved with the autopilot, which is something that appeals to the squeamish Interrogator very much. And yet the electrical impulses are thorough and irreversible. The Interrogator describes the process of removing a personality with the metaphor of a pencil (the creative scribblings of an individual mind) and an eraser (the electrical impulses invading the brain):
They continue lockstep in this way, the self and the state, coming closer to one another until finally the pencil and the eraser are almost one, moving in sympathy, the line disappearing even as it's laid down, the words unwritten before the letters are formed, and finally there is only white. (317)
For the Interrogator, there is beauty in the chase. While the personality struggles to maintain itself, the impulses of the autopilot configure themselves to seek and destroy. It's so customizable. So neatly done. The image of the eraser, which chilling once we realize what it's doing, is still sort of appealing: it creates a clean workspace, a blank slate on which a new text can be written.
The Interrogator clearly wants us to see only what is admirable and lovely in the process—hence the metaphor. In this work, figurative language is generally used to cover unpleasant realities (think of the "white flower"), so it isn't surprising to see the Interrogator manipulating that kind of language so well here. He sees the self/state, pencil/eraser combos not as opposites but more as whole entities: the individual, in his mind, should be allowed to exist outside of the state.
By forcing individuals to submit the domination of the state, the Interrogator's actually creating an army of people just like him: nameless, with no personal story, and with very little desire to challenge the official narrative.