The Rape *Spoilers*
I know there are other threads about this bit I thought Id weigh in with my own theory.
The western was all about the good guy being the good guy through and through and while a nice thought it was heavily overdone and I'm sure Clint Eastwood himself knew that the old west probably wasn't so cut and dry.
A lone stranger who had no qualms about shooting any man in cold blood would probably not be the nicest person and would more than likely have other bad traits to his character. I think the rape does the job of removing the glamorisation of what these films were really about and that is killing people for if you remove the respect for the protagonist then you see all the other things he does in a different light.
Just to add yes it was a rape, this was cemented in the fact that she tried to shoot him in tears and it's not something that should ever be swept under the carpet so I'm glad it was included because I guarantee it will disgust more people than it will excite.
The fact that the stranger left town at the end exactly the same as when he came in with no change of heart or resolution hit home again that just because someone has the power to help you it doesn't mean they are a good person.
Clint Eastwood is no idiot and he likes to turn a concept on it's head and making the good guy a bad guy is one of the simplest ways to do that. It certainly made me view the film differently than any other western I've seen due to that awkward feeling of "Errmmm who do I root for?" and I have the feeling that was the intention all along.