I guess I kind of live in all three opinion worlds. All of my real kilts are in my clans tartan (traditional view) but, I like a few of the non clan tartans and may buy one some day ( the "wear what you want" idea).

However, I may buy a kilt in the Macdonald tartan and wear it to honor that great clan. If I study the clans history, I would be able to tell people who ask, about all the awesome things the Macdonalds have done.

Through my studies, I have learned that per 45, particular tartans were not "assigned" to a particular clan and wearing what ever tartan you like is the most traditional thing you could do.

To each their own.