Native American people may have a history of being politically marginalized, but their abuse has not come from caricatures and nomenclature.
The African American community would be perfectly entitled to take offence if a sports team adopted a caricature bearing an African American likeness as its mascot. African American features were deliberately mocked and caricatures were used as a repressive tool to dehumanise and marginalize the community.
However, these have not been employed as tools to marginalize the Native American community. Therefore, the use of a Native American figure as a team’s mascot does not carry historical baggage that would make it offensive.