while I feel the same way, that a kilt is clothing, personally I'll wear tartans I am associated with in some way. MacTacish as it's my clan, Irish Saffron as I've got TONS of irish ancestry ( and I'm from south of Boston),the UK because I'm an american, and the Blackwatch because many of the clans I can trace my roots to were at Culoden, or some other major scottish/english battle, and I honor them.

I think if you wear a tartan you are not associated with, you might want to learn a little about that clan, mostly for when people ask questions, but also to enrich you own understanding of the various clans of scotland ( or wherever the tartan is from).