Many Christian pacifists think that participating in governmental positions like the president or congress are compromises for one's Christianity. The president is the commander in chief of the military and congress passes all sorts of forceful legislation and legislation that allows for harm to come to others (self-defense laws, voting to go to war, etc). It seems like a shirking of duties, then, if pacifists are unwilling to participate in government to a certain extent.
There are several problems with this accusation. The first is that pacifists acknowledge that the Kingdom overrules the kingdom. Their primary responsibility is not to compromise the lesser for the greater. It doesn't matter if people think they are shirking responsibilities.
Second, a participation in lower government is still possible. There are all sorts of levels in which a pacifist can do great good (public education, healthcare, federal benefits, etc). Why does one have to be willing to serve as a higher level official to be considered a beneficial participant in the land?
Finally, I hear many conservative Christians bemoaning the onset of what they view as growing socialism in the United States. They hate that we have, in their minds, become a welfare state. But then, sometimes in moments of self-reflection, they acknowledge that the government has likely gotten involved because the church wasn't handling her own business. In Rome the secular government acknowledged that the Christians were taking better care of her people than the government was. We don't have that same problem in the States. Many Christians acknowledge that we would have less intrusion, waste, and handouts from the government if only the church would value life and participate in self-sacrifice more, Unfortunately, I often hear from the same conservative Christian group that legislation is the answer for the moral ills in the United States. So what is it - a bottom up approach or a top down one?
I would argue that a marriage to the state, an embracing of legislation, and a top-down approach is not at all the answer. Early Rome had gladiatorial events, temple prostitution, state laws requiring worship of Caesar and the gods, slavery, and the list goes on. The Roman state changed for the good by leaps and bounds before Christianity began to be legislated, when there was a bottom up approach. When Christians really lived as Christ taught them to, that seeped out of their everyday lives, into the local communities, and into the nation - long before any Christian was an emperor. While just war theorists can embrace this same sort of notion and recognize the importance of the church, the approach of Christian pacifism highlights and underlines this notion. Christian pacifism places the lever of power on the Church, the gospel, and the Christian life rather than armies, governments, etc.