Esther,
I know the mitzvos of Purim!
and it DOES says ‘chayov inish ….’
In fact, its been said that a person should get drunk to the point where he doesnt know the differnece between ‘Orur Homon’ and ‘Boruch Mordechai’
Every Mitzvah is holy, and in the case of Purim , there obviously is allowed to be ana element of Kalus Rosh.
As far is your story is concerned, this person was Mivayish someone in public. We all know how devastating the consequences of that could be, and there is no inyan of embarrasing someone else. But making a ‘clown of oneself’ is obviously permissable within limits. What does ‘vinahapch hoo’ mean? Dressing up, parading in costumes is obviously ‘letzonus. Ofcourse, its a holy idea and a mitzvah on purim.