As has been stated, the Kilt was a 'Highland' garment and Lowlanders would in some cases make fun of Kilts. However it is most certainly a 'Scottish' garment now.
Don't forget how many Highlanders moved to the Lowlands!
My family were from the Highlands as far back as we could trace until my grandfather moved to Perthshire and then Glasgow while he was a boy. The rest of the family are still in the same area of the Highlands and the old farm still has the same name!