This guy was stuck up in his bigoted ways and this mistress knew that she had to dominate him and teach him a lesson he had never been taught before. That is why she opted to knee him in the nuts as well as to trample him, make him lick her muddy boots and also facesit him. He had never been as humiliated as he was that day and he had to rethink his bigotry.
When this mistress realized that she was dealing with a girl who was too much of a gossiper, she felt that she had to do something to punish her and make her learn to stop gossiping. So she made her carry her and then she forced her to drink muddy water and to carry her like a human pony. The pain and humiliation made him to change and do better.
This guy had promised these mistresses things that he did not do. The mistresses were angry at him as they were banking on him. He had to learn his lesson the hard way and never do that again so they trampled him together at the same using their high heels. He was in a lot of pain as he had to handle all their combined weight. It was brutal but he had no choice.