Mistress Annalise felt that this guy was being ungrateful and she did not want to encourage such behavior. So she punished him using her shit and she made sure he would never do such a thing with her again. She had helped him out in a major way but he acted like it was something small. Before the help, he was begging and crying to her but he had forgotten that as soon as he had been helped. So the mistress took a shit on him and he learned his lesson.