Why is Dr.Bledsoe so angry with the narrator?

Bledsoe demands to know who told the narrator to drive where he did, shocking the narrator even further. He cries out that he is lying, and calls the narrator "nigger," enraging the narrator by using that word. When the narrator denies lying, Bledsoe reveals that he thinks the vet doctor is behind the drive and interrogates him regarding the man, noting that he will have to investigate the dangerous patient soon.