Never been confronted with that situation. Sometimes living in another country with no Halloween is a blessing... But I migth have felt a little hint of sadness, like "oh, if they only knew"... But I think mostly I would have taken it as a silly costume. Depends how far the wearer of the costume took the act. When I see comedians making fun of MI, it sometimes bothers me. I usually think to myself; - really, really, that is the best joke you could think of?!