Don't forget me and my limited awareness of Scottish clans.
As for the last part, it mirrors what happened to the R-word. People who claimed to be 'Native American' try to take this slur as a badge of honour. Well, it would have been if not for the newspapers back in the mid-19th century! What it's supposed to be a simple identification of Natives in general is now turned into a pejorative word used to refer to them doing bad things.
And sure, 90% of them won't give a single damn about it. But you'll still see other people who think the nickname is now an outdated, racial slur. Yet, when you look at the comments on Youtube about this issue, you won't know if the commenters in the comment sections are really Native American (or at least have ancestral blood to any Native tribes). At any point, it's probably racist white gammons pretending to be part of an ethnic group when they shouldn't be.
The difference between the Clan and the R-word is that the former has more than one meaning, while the latter just refers to one group of people. In a horrible way.