It's worth wondering how the secret society depicted in the film would function. For example they place a great value on seeing his face, some other people in the party are unmasked, most are masked.
Imagine if you were there alone, not known to be there by anyone else, and you see your wife there, fucking another man.
What if you are bound to silence through threat of death to not react or show signs of mistrust afterwards?
Could be a test of social strength, or a powerful insult in some social language that the rest of the world is blind to. A great deal of leverage and control over people could be achieved through this.