If people can’t get over Johnny Depp portraying a native american in an offensive way in The Lone Ranger then how do these same people enjoy any story? Pretty much any piece of fiction is rife with inaccuracies and factual errors that may be racist, dehumanizing, etc.
But really, it’s a movie. If...
We can be mad about it because our people are being discriminated against. There are plenty of Native American actors who could have played the part. Not only are we being discriminated against but stereotyped. So yeah, I think being angry is justified.