I don't get this. He says he wants to portray a more "realistic" version of history. But he's really making his own value judgements about what that history should be. He's taking the position that the English settlers were wrong to come to America and settle this land. He's taking the position that the Indians were just peace loving people, living in harmony with nature. He's injecting a certain point of view into the story of Thanksgiving and the overall settlement of America by Europeans. He's not being "realistic" as such. He's taking sides and presenting a viewpoint that he agrees with.