Mistress Lucy does not like to be interrupted. When this guy did it, he pissed her off and she did not like what he had done. That is why she had to act the way she did and to beat him for what he had done. The mistress went ahead to make him do things her way and she had him lick her asshole as well as eat her shit.
Mistress Lucy had a wayward husband and she did not want him to think that he could go on doing what he had been doing without her doing anything about it. She had tried to talk to him but it seemed that talking to him was not working. So she had to change tact and she used her shit to do it. It worked and made the guy change for the better.
This guy had tried to ignore mistress Lucy and yet he was the one behind the issues she was facing. She did not like the pretense from him and she had to act as quickly as she could. That is why she chose to shit on him and humiliate him as cruelly as she could. He learned his lesson and he never tried that again with her or anyone else.