I'm assuming, since I can't see the article at work, that he's just wearing a "regular" kilt of some variety, in which case calling it "fancy dress" (that is, a costume, and in the Dracula for Halloween, not in the "it's our national costume" sense) is offensive. Like many kinds of trousers, a kilt can be "smart" or casual or downright sloppy depending on the accessories.

Now, if he has a swath of plaid fabric draped around him, is barefoot, not wearing a shirt, has his face painted, and is festooned with highland weaponry, then I might agree that it's fancy dress and not entirely appropriate. (You know you've seen these people at highland games. Don't deny it! ;) )