This realtor misled lady Scarlet to take a unit she should not have taken just for him to get a commission and that angered her when she found out. It was too late and she could not do much about it. But she had to punish him so that he did not do that someone else. That is why she had to make him eat her shit. He had to.
Lady Scarlet felt like this slave was deliberately doing things to piss her off and she did not want to happen again. So she did what she does best and she used her shit to make him stop. The mistress shocked him with her punishment and he had to eat the shit that she wanted him to eat. That made the loser learn never to take any for granted again.