Kevin, yes, it is costly, in a way. The accusations and bitterness that come from other Christians with taking this stand is formidable. And sometimes it is enriching.
I work at a small Christian TV station with two highly Conservative Christians who are also retired military. We have had many, er, spirited discussions over a number of issues, including this one. We all somehow manage to keep civility and kindness at the fore, no matter how strongly we disagree. And that has helped us all grow.

The "What about Hitler?" argument was interesting. Then there was, of course, the supposed scriptural support for war by citing OT battles. The answer to both of these is so simple it defies acceptance. If not for Christians engaged in politics instead of advancing the kingdom, there would have been no rise to power for Hitler or WWII. What if you declared a war and nobody showed up? 
The kingdom of God in the OT was a physical one and the temple of God was a structure. Retributive (eye for an eye), not Restorative (7 x 70), justice was in play that demanded physical punishment.  A tutelary period. God tried to discourage the top down government of kings but allowed the Jews the consequences of their desires.
The NT is different: Our kingdom is not of this world. We do not fight with the weapons of this world. We do not return evil for evil. One rule, as found in Romans 13 (of all places): love your neighbor.
When did this shift take place? As you know, after the resurrection. Of course Jesus could send out his apostles with a  sword, yet might that have been to demonstrate that they need not rely upon it, a useless weight to carry? And might not his instruction to carry a sword suit their progress in truth? Another necessary lesson?
Jesus did not look to dissuade the Centurion from his duties as a soldier. Is it necessary to say that Jesus could read his heart, this one who showed the greatest faith? With such a demonstration of faith, his heart belonged to God; he would act accordingly in the future and such actions might 'turn" others away from violence. All maybes yet why are these things used so assiduously as solid ground for being armed combatants in war?
Nothing of the New Covenant supports war or political partisanship or patriotism for a worldly power. While it does, in fact, speak plainly against such activities in any number of verses about "worldliness."
I just needed to say all that for me.