Why did the courtroom erupt into a commotion?

The courtroom erupted into a commotion due to Bob Ewell's language on the witness stand.

Mr. Ewell looked confusedly at the judge. “Well, Mayella was raisin‘ this holy racket so I dropped m’load and run as fast as I could but I run into th’ fence, but when I got distangled I run up to th‘ window and I seen—” Mr. Ewell’s face grew scarlet. He stood up and pointed his finger at Tom Robinson. “—I seen that black nigger yonder ruttin’ on my Mayella!”

So serene was Judge Taylor’s court, that he had few occasions to use his gavel, but he hammered fully five minutes.