At some point the past is the past, be it Mountain Meadows or The Trail of Tears. 

 Lets face it:  "White" killed "Red," "Mormon" killed "Non-Mormon," and so on.  But Roman killed Samnite, Aztec killed Maya, Mongol killed Chinese, Crusader killed Muslim, French killed Prussian, Teuton killed Lithuanian, and, for every one... vice versa.  There's no easy way to describe the colonization of the Americas without mentioning mass murder, disease, and cruelty.  But there's no way to talk about almost anything in history without mentioning mass murder, disease, and cruelty.  Today's winners are tomorrow's victims. 

If we don't move beyond back-and-forth accusations about relative guilt, we will end up in a state of anarchy, each bent on taking "justice" from every other person because of the actions of our ancestors.

Let's study the past, face the horror, and move past it:  let's learn, after all!