Breaking News on team name

[JoeRedskin]

Originally Posted by Giantone

https://en.oxforddictionaries.com/definition/redskin

Per your cite: "The term originally had a neutral meaning and was used by North American Indians themselves, but it eventually acquired an unfavourable connotation."

If the natives used it to describe themselves, even today it is used by Native Americans as a team mascot, and there has been no poll (that I have seen) showing that a majority of Native Americans consider it a pejorative, then how did it "eventually acquir[e] an unfavorable connotation" except by those not of the group at issue?