Quakers recommend that, in our relations with each other, we should strive to respond to "that of God within everyone." In my own thinking, I have always related this to a supreme principle of respect. At least part of respect includes believing that everyone is capable of goodness. And at least part of the recommendation to look for and respond to "that of God" within everyone is also to assume that everyone is capable of goodness.
Immanuel Kant proposes something similar in his moral theory. One formulation of his "categorical imperative" is "Act in such a way that you treat humanity, whether in your own person or in the person of another, always at the same time as an end and never simply as a means" (Grounding for the Metaphysics of Morals, 429, trans. James W. Ellington, Hackett Publishing Company,  1981).
I have been reading the stories of the women who went to Dr. Tiller for care and they are nothing short of breathtaking in the level of trauma the women he helped were in.
From Joss Whedon's Angel:
we will never win. not completely. that's not why we fight. we do it because there are things worth fighting for.
So I'll continue to fight without resorting to violence, in the belief that compassion is the right way to fight. sigh.