Mistress Alexandra had no beef with this guy. She was paid to humiliate him and she did it without caring. She had been given some good money and she did not hesitate to use her humiliation prowess to dominate and humiliate him. So she facesat him and choked him with her ass before she chained him and spat on him for her own fun even though she was punishing him.
Mistress Alexandra does not like it when people disagree with her and especially if it is people she considers beneath her in the pecking order. She felt that this guy was trying to undermine her authority and that is why she went ahead to strip him naked and whip his bare ass. This was after she had turned him into a sissy because she felt that it suited him well.