The Kilt is a costume.....

[Riverkilt]

Everyone's an expert about everything.

I like the common two word response to people who've insulted you.

Look them hard in the eye and slowly and clearly repeat the beloved words to their face.

[jkane]

When I am at a loss for words, I simply agree with them. In this case I would just say yes it is a costume and go about my business. If I like the person and want to have more conversation, I might ask why do you want to know? They are trying to get a rise out of you. By agreeing, they loose their steam and then begin to accept it as just who you are instead of something to tease you about.

Relax, be calm, and just act like you already know what they think and don't care either way for their opinions.