The film says something important, that the US calvalry in the 1880's behaved with appalling savagery against Native Americans. It shattered the complacent myths of the US Western and its false view of the real history of the West as some kind of civilizing mission and not a brutal occupation and colonial land grab. It came out shortly after the notorious Mai Lai massacre by 1960's US ary troops where they also killied women and children quite deliberately and wantonly.
But the film is so uneven that the criticism of the final scenes do seem somewhat justified. One is glad it was made because the US public and the world needed a corrective to the gallant 7th Cavalry ideas usually pushed in films but in many ways its hardly a serious film. So its a serious message in a rather thin wrapping but a filn noone who likes Westerns or exaples of revisionist history should miss.