I see where you're coming from, but for the purposes of language, I'm not aware of Mormon being a slur, and it's probably the most widely known term used to describe people in the LDS church. It's been only a few years since the church themselves called themselves Mormons:
A person changing their name and a tribe changing their name is not exactly comparable, but I can see there is some gray area. I guess if people in LDS really made a big deal out of it, I'd change the way I referred to them.
Exmormon here, and op is full of it. We used to call ourselves mormon for a long time, and many of my friends still active were like whatever I'll disregard that "commandment" to not use Mormon as a term... I mean there's still a pro-mormon subreddit called mormon, and until 2016 the church had mormon.org with multiple people sharing their testimonies using the phrase "I'm a mormon".
This is just a corporatocracy trying to "rebrand" under new management. Nothing more.
https://en.wikipedia.org/wiki/I%27m_a_Mormon
A person changing their name and a tribe changing their name is not exactly comparable, but I can see there is some gray area. I guess if people in LDS really made a big deal out of it, I'd change the way I referred to them.