What sentences give away the theme?

The first thing to do with this question is figure out which them you are trying to find quotes for. This story has more than a single theme, so start with picking a theme. I tend to emphasize the theme of dehumanization in this story. The boys are treated like animals and exist for the pure entertainment purposes of the wealthy elite; however, the nude woman is also treated as an object that exits merely for the titillation of wealthy white men in attendance. A supporting quote would be the following quote.

And all the while the blonde continued dancing, smiling faintly at the big shots who watched her with fascination, and faintly smiling at our fear. I noticed a certain merchant who followed her hungrily, his lips loose and drooling.

A number of the men eventually start groping her, and she is forced to flee in sheer terror. Once the boxing and fighting match begins, the narrator flat out tells readers that he felt as if he had no dignity. It has been taken from him just as his sight has been taken from him with the blindfold to make the boxing match that much more hilarious for the drunken onlookers.

Blindfolded, I could no longer control my motions. I had no dignity.