When I was a kid, my family used to dress up as Pilgrims and Indians for Thanksgiving. I was in charge of the costumes; black construction paper hats complete with tinfoil buckles for the Pilgrims and bands of construction paper with real feathers for the Indians.
The Thanksgiving holiday celebrates the bounty of a good harvest and “remembers” how the members of the Plymouth colony did not have enough food to survive the winter and were supported by the Wampanoag Indians.
Dressing up in the historically incorrect stereotyped costume of an oppressed minority group is, well, racist. It embraces the cartoon version of people. It reduces a group of people with varied customs, languages, culture, and dress down to a few feathers taped to a headband. Although this piece is about Halloween costumes, the same arguments apply to Thanksgiving dress. This incorrect perception about Indian dress is so common that it’s a TV trope.
We can all enjoy the holiday without perpetuating stereotypes. Food and family will be there, even if your “Indian” costume is not.