Mistress Infinity was enraged when she learned that this slave had been spreading rumors about her. He had the guts to divulge her secrets, despite assuring her that he would not. He had broken her trust and for that, she was not going to forgive him. She was also not going to forge what he had. Best of all, she was going to punish him, and she did this with her shit fetish which she used to teach him a lesson.
Mistress Infinity and her friends needed to teach her slave the consequences of his actions. He was used to overstepping his boundaries, and he always assumed that there would be no consequence thereafter. But they knew that this was not the case. So they had to punish him for it, and they did this to teach him a lesson. It worked like they had wanted it to. He did not believe it as the mistresses chose to make him eat poo and recorded it as he did.