The documentary film-maker Ben West hails from Washington DC, and thus grew up rooting for its football team. He wore the gear, watched the games, cheered on an organization named for a slur against Native Americans. Even as a kid, West, who is Cheyenne, felt the dissonance between the team he rooted for and the supposedly “honorific” idea it represented – that Native Americans were a symbol of war and violence, a costume to be donned in the name of gladiatorial sport. “Is that me on that helmet?” he recalled thinking. “Is that me on that jersey? And does that...