How is repetition used to show the narrator's shock when Dr. Bledsoe calls him a "nigger"? InInvisible Man

The narrator repetitiously thinks to himself, "He called me that."

"It was as though he'd struck me. I stared across the desk thinking, He called me that . . ."

"That, I thought, noticing the throbbing of a vein that rose between his eyes, thinking, He called me that."