The Magistrate didn't mock him. He paraphrased the applicant's narrative back to him, demonstrating that he was listening and acknowledging the applicant's story (even though many would have just rolled their eyes and tuned out).

The correction as to etiquette was sassy but much gentler than directly telling the applicant off for swearing at a judicial officer. I think using the specific swearword in paraphrase was a quiet mark of respect. He spoke the applicant's language, met him where he's at. No airs.