I am not going to dive into international politics, capital punishment or abortion.
I was raised by a self-described pacifist. Pacifism, rightly, is not passive. The root is peace. You can defend innocents and be a pacifist. You can protect your wife and be a pacifist.
The question a pacifist ought to ask is not, “what should I avoid doing?” but rather, “How can I act?” Our models for modern pacifism include Martin Luther King Jr., Gandhi, and many of the early pro-life workers. You cannot look the other way and call yourself peaceful. Neither can you address hate with hate. “Hate cannot drive out hate; only love can do that.” When you defend an innocent it cannot be out of hatred for the aggressor, but must instead be out of love for the innocent. And indeed, though it is just to hold the aggressor accountable for his actions, it is also necessary to forgive. By forgive, I certainly do not mean that you should not ensure that he is held accountable to the full extent of the law, I mean rather that you should love him. Want salvation for him.
The problem is that it is difficult to know where the line between necessary defense and peaceful address is. It as a problem that every Christian, whether a self-described pacifist or not, struggles with. There are many issues- some have been raised in this discussion- where an evil cannot be ignored. The question then, is how to act. There is legitimate debate on that question. The true pacifist, however, will not say that he cannot act but that he must act with peace as an end. He will try to stop the rapist with minimal violence. He will see to it that the rapist is held accountable in law. There is nothing peaceful about watching a violence take place and not acting. True pacifism is courageous. Think of the freedom riders who faced terrible violence. Think of Christ, who suffered and died. (Perhaps some will be insulted that I claim Him as a model for pacifists, but hear me out.) The true pacifist always acts. He may suffer violence for his cause, but the cause must be non-violence. He does not, therefore, watch violence silently. He chooses his actions carefully, and he knows that violence begets violence. He must also know that inaction is gravely evil and sometimes non-violence means using less force than you would care to and only enough to stop a violence.