The genocide of indigenous Americans was evil.
During difficult times, the principle of choosing a day of thanksgiving rather than one of mourning – of looking forwards and choosing hope rather than backwards and choosing despair – is good.
Thanksgiving isn't necessarily religious. It's not really nationalistic. Thanksgivings were celebrated long before Columbus, and the US holiday wasn't formalized until Lincoln did so with reference to ending slavery.
I love #Thanksgiving. It's the only holiday I have left; all the others have been ruined. Please let me celebrate Thanksgiving.