If you go down this road, many other nicknames are offensive, not just Indian nicknames.
Boston Celtics is offensive to the Celtic people.
Pittsburgh Pirates is offensive to real pirates.
Pittsburgh Steelers is offensive to steel workers.
San Diego Padres is offensive to priests and all clergy.
Minnesota Twins is offensive to real twins.
Milwaukee Brewers is offensive to real beer brewer workers.
New Orleans Saints is offensive to the Catholic Church.
Seattle Mariners is offensive to sailors everywhere.
Dallas Cowboys is offensive to real cowboys.
Texas Rangers is offensive to that law enforcement agency.
Buffalo Bills is offensive to Buffalo Bill Cody and his memory.
Not to mention, all of the animal nicknames are offensive to the animals, and thus, the PETA crowd can have their mock outrage about all of those.
Gaia is offended over the Oklahoma City Thunder