Miss Lith did not want to think that this guy was uncontrollable. She had to dominate him and she did it with her shit. She felt that the best thing to do to him was to shit on him and to make sure that he also drank her pee. That is exactly what she did to him and she got what she wanted from him at the end of it all.
Mistress Anna was angry at her slave and she wanted to cruelly punish him and force him to leave her house. She wanted him to quit out of her cruelty as opposed to chasing him away. So she took a shit on his face. She forced him to eat all of it and he had no choice but to do it. He had put up with other punishments, but this one was excessive and he quit.