If it was so horrid for somebody to be wearing it why would it be available. I wear a Scottish National Tartan but I am not a Scottish National.
Actually, the Scottish National, the Irish National, Welsh National, etc. is meant for anyone is a citizen of that nation, or who is a descendant of someone who came from there. If people are giving you heck because of that point, then they are in the wrong. Technically, it is a "district" tartan, and may be worn by anyone who lives in that district or has a connection to that district, however small.

Cheers,

T.