David, I know that the invasion of Europeans here was not great for Native Americans, and I can see why Columbus Day would not be something you'd want to celebrate.
But Thanksgiving? To me, Thanksgiving symbolizes one of the few bright spots in the history of European- and Native American relations. It's about celebrating friendship and good times. Granted that celebration may seem like small potatoes compared to all of the harm that followed, but nevertheless there's nothing negative about the holiday itself, in my view.