Indian related policies are substantive and completely align with the goals of her campaign, as they focus on correcting long-term, systemic injustices in American society. Foregrounding the unique problems levied on marginalized peoples in America, including Native Americans, helps to make people understand just how fukked up the system is and likely to want to fix it. Rescinding those medals of honor is a symbolic gesture to demonstrate what type of country she thinks America should be; one that doesn't celebrate genocide, which is an especially relevant statement in this era.
In terms of political strategy, the goal isn't to make Trump stop the racist Pocahontas attacks, it's to provide Liz with a counter-punch that redirects that negative energy into something positive.