While some might balk at the idea of Robert Taylor playing an American Indian, such casting was pretty typical of this era--with folks like Rock Hudson and Paul Newman cast as Indians as well! Plus, while the casting is poor, the film does have a lot in its favor. The biggest plus is that the American Indian is portrayed VERY sympathetically here and is a film about intolerance and prejudice--and makes some excellent points to counter the prevailing "evil and stupid Indian" image many films of the day. Plus, although Taylor is an Anglo with an aquiline nose and blue eyes, the film manages to have him appear rather Indian-like--and his craggy middle-aged good looks helped--along with gobs of skin paint! I cannot speak for American Indians, but I assume most would appreciate the film's message and overlook the casting--as there simply wasn't any better sort of film about them made at the time--and very, very few since.
The film begins with Taylor returning home after several years absence serving in the Union army during the Civil War. Along the way, he developed a bit of naiveté and assumes his being a sergeant in the military and living out the White American dream that he'd be accorded respect and equal treatment at home. However, there's an ill-will brewing and instead of receiving honor for his service (which had earned him the Medal of Honor--the nation's highest military award), he will face a lot of unreasoning hate. At the heart of this is a scum-bag lawyer (imagine that!) who is bent on stirring up the Whites against the Indians--mostly so he man make himself rich in the process.
I could say more to the plot, as there is quite a bit more to the film, but I really don't want to spoil the film. Suffice to say that it is very well written--mostly because it is NOT a movie with a clear message that the settlers were all evil and the Shoshone were perfect and noble. I liked this, as both sides had a point--though the Natives clearly were having their rights cast aside in the process. The characters, as a result, were multidimensional and interesting.
Overall, if you are a bit tired of cookie-cutter westerns and are looking for something a bit different, "Devil's Doorway" is a pretty good bet.