In my humble opinion I started wearing "the kilt" was a replacement for a pair of blue jeans..
I go casual or dressy depending on the weather and the ocassion.
Among my collection of 16 kilts one is black, one is kelly green and one is saffron.
I don't consider them any less of a kilt than my tartan kilts. So I think your friend need a reality check and some education when it comes to kilts.
Robert "the kilted" Lamb