Mistress Tiffany was pissed by her slave and she was further angered by how unrepentant he was. She was pissed about it and she had to make sure he learned to repent for his wrongdoings. So she used her dirty boots to punish him. And she made sure he learned not to do the things that angered her. As she crushed his head with her boots, he regretted why he had done so.