What, if any, dress code or written dress expectations are in place at your place of empleyment and your level of employee? If none, your supervisor is in critical violation of your civil rights (unless your kilt was somehow dangerous in the workplace)
I hate to belabor the point, but this is not a civil rights violation. Not in any legal sense. It's a dress code issue, nothing more. There is no established legal "right" to wear the kilt at work in the private sector. Scotcop would have no legal standing to even threaten action over this incident. Not only does he have no legal precedent to back him up, but he doesn't even have any damages to claim. It's not like he lost his job. He just got a verbal warning.

Invoking the term "civil rights" really does not apply here, as much as we would all like for the law to protect our inalienable right to wear the kilt wherever we choose.

Scotcop, I don't think you mentioned whether the manager knows that this guy sent you home and berated you. Was she present at the store when this happened? If so, did she just allow it to happen despite her previous permission?