Martialist Christian
I practice martial arts for many of the same reasons as other people - to stay in shape and to hang out with friends. However, I ride a bicycle and hike for those same reasons. If exercise and friends was all I am after, I would stick to riding and walking (less bruises). I practice martial arts to learn how to hurt people.
... And yet I am unconflicted as a Martialist Christian.
The Christian Warrior is not only allowed in my ethic, but it thrives. What if I were being hurt? What if it was my girlfriend, or one of my kids, or friend who was in trouble? I would want someone to help - to fight - and not just standby and watch. Christian love requires us to imagine ourselves in another's place and to act. In the New Testament parable of the Good Samaritan, the Samaritan was good because upon finding the man after he was beaten and robbed, he cared for him. Would he have still been the hero of the story, if he had stood by and watched while the man was beat down, and then care for him? No!
Happily my life is not filled with bad guys who are constantly attacking my family and friends. However, it is satisfying to know that I can do a lot as a Christian to help the people around me - including defend them.