Mistress Delvia is a BBW girl. And she gets made fun of a lot. But this guy said even nastier things to her and made fun of her. She was so pissed at him specifically that she had to punish him. This she did with her farts and made sure that he was so humiliated and in so much pain that he would never say that about someone else again.
Lady Phoenix and mistress Delvia had an admirer. The guy loved girls with big asses and they had that in plenty. So he could not stop looking and admiring. The mistresses took that chance to dominate him and have fun at his expense. They had him see their asses but besides that, he was made to smell their farts. He actually did not mind as he got to see their asses up close.