I wish I could give a fuller response especially since I'm taking a course this semester called "religion and violence".
Cavanaugh's essay "The Myth of Religious violence" is pretty good. Just to get you thinking about assumptions we have.
There is also "Just War as Christian Disicpleship" by Daniel Bell.
In short, I don't think complete non-violence is always what we should aim for. Even while saying "turn the other cheek" I think Jesus means an attitude more than an actual action. After all in John 19 he doesn't turn the other cheek-- he rebukes those who struck him!
Rather than complete non-violence, I think we need to regulate our violent action by our belief in Christ. That is, violence isn't considered the lesser of two evils but rather a way that is sometimes necessary to stop evil. It is not that we should aim for violence but rather that violence isn't a sin but the malice, anger, hatred and vengeance often associated with it is.
So, I think we need to take it on a case-by-case basis. Will violence stop this evil? In short, a "just-war" attitude from violence but not as just-war currently stands-- we need to really inject God back into our thinking to regulate and impact our behavior in every area of life.
So my answer is, YES if someone's attempting to rape someone else I WOULD step in to disable them-- not kill them vengefully-- but disable.
That said, I'm a really small wimpy guy. So I don't know how much I would or could do.