What is ironic about the narrator's attempt to get rid of the coin bank in Invisible Man

The narrator notes that in his hands the bank looks more like it is being strangled than like it is smiling. It then breaks apart spilling its coins as the narrator yells at his neighbors to stop acting like uncivilized rural Negroes. He destroys the object that he identifies them with but more importantly he attempts to destroy the fear inside of himself. The bank is a metaphor for the recurring nightmare of his laughing grandfather. It is a character yessing the white man, or "acting the Negro", and on the morning of his new role in society, the narrator cannot stand being reminded of this attitude.