My take on it is that there are a number of tartans that are not clan tartans which, due to that fact, cannot offend any pretender to a clan.
I am a strong believer (my own value system and without prejudice to anyone who disagrees) in a degree of entitlement in your choice even if that is tenuous.

I can only find one tartan I can lay a claim to and it just so happens that I like it.

I can understand people getting precious about it but I also think that the Victorians have a lot to answer for with their gross and misplaced 'propriety'.