All those things were around before you and you didn't invent the color white.
The Navajo invented the name Navajo and they have a right to protect the value of their brand, particularly as they have a law backing them up. I think they have a good case.
Can you prove or demonstrate that the Navajos coined the term “Navajo”? After all, the Irish didn’t call themselves “Irish”, the Germans don’t call themselves “German” and the Scots were name that by the Romans.
Just asking
The word "Navajo" comes from a Pueblo language word for "fields beside a ravine," and was adopted by the Spanish to refer to the people who called themselves the Diné. "Navajo" isn't even from the same language group, since they speak an Athabascan dialect and the Pueblo language is from the Kiowa-Tanoan group.