The Kilt is a costume.....

[Nighthawk]

Yeah, but you have two eyebrows.

Only because I shave the bridge of my nose...

[Whidbey78]

Only because I shave the bridge of my nose...

I can relate. People think I'm growing a mustache, but I just keep forgetting to trim my nose hair. Sometimes I hate being a mammal.

[bear]

I first said, "Kilts are garments, not costumes!" to show people that you can wear your kilt whenever you choose and how you choose, that a kilt can be worn for more than weddings and funerals.
It was a response to traditionalists telling me I was offending their culture.
Analyzing the words is moot.
Kilts evolved as a garment for a very long time before they were declared a national costume. And guess what? They're still evolving!