Yeah, I live in Arizona, and there are many Natives here. (That's what I hear them calling themselves -- Natives, Indians, or specific tribe names.) However, Quora has an international audience, and some people in other countries might not know what these terms mean. That's why I said "Indigenous Americans" so that people in other countries would know what I'm talking about.
As an autistic person, I am cautious to avoid offending anyone. My very existence seems to be offensive to some people, so I do my best not to add any additional offenses. People say, "Just relax and be yourself." That may work for neurotypicals, but it did not work when I did that for a while. I was scapegoated, accused of things I wouldn't dream of doing, and a complete outcast. Humans are obligate social creatures and being an outcast can impact survival. I saw this firsthand. So now I conduct myself like a polite guest in this society, and in return, they let me live.
So when someone from an ethnic or social minority says, "Don't say this; it offends us," I comply. That's because I am also a member of a marginalized group, and I know that words can hurt.