Mistress Madison facesat on this guy because he had pissed her off but as she did it, she got the feeling that he was enjoying it instead of being humiliated and dominated with it. He could feel and smell her pussy and she knew that was the reason he could not feel humiliated or dominated. So she changed the punishment and made the guy drink pee and he was humiliated and dominated.
Mistress Madison wanted to dominate her slave and teach him some better manners as she felt he was lacking in that department. The mistress had to make him receptive for what she had in mind for him and that is why she had to facesit on him. The slave did not want another punishment and that is why he changed so that they would not have any issues between them.