First,

I agree with beowulf67; the other person was trying to use you in your kilt to achieve their own ends of wearing jeans. Unfortunately, an inappropriate management response has exploded the situation beyond reason and it has now landed on you.

Take a deep breath, know the policies, become best friends with HR, always be polite and sincerely constructive when educating others about the kilt. In this situation, the kilt is a red herring distracting others from the issue. And most of all, do your job.

I've found the higher educated and more professional the office, the more subtle the discrimination becomes. A calm, focused approach always makes the others look more hysterical.