For the most part, I do agree that war is evil. However, I respectfully disagree that evil is necessary. Anything that is evil is of satan. The war that you speak of in heaven was against God's enemy. This is why I say "for the most." Any war that is fought against God's enemy (satan) is not evil. The problem is many Christians (and non-christians) have claimed to have fought for Christian reasons, but in truth, their reasons had nothing to do with God. I do not know much about Islam, but I would suspect that those who strap bombs to themselves and kill others are not truly doing what their god requires. I repeat, I do not know much about that particular religion.
As for Christians being soldiers and police officers, I have given much thought and prayer to this very issue. I am a retired military person, so this is very personal for me. When I spoke with a trusted minister concerning this, he asked me what obligation did I make. The answer was to protect and defend the Constitution of America against all enemies. He was trying to make the point that I did not agree to committ murder. My response was that this was to defend America's enemies, not God's enemies. I went on to ask what would have happened if America enemy became God. He said that nothing came before God. His point about not committing murder implied that killing in battle is not the same as shedding innocent blood. While I do agree that there is a difference, I am not sure that makes it all right.
If America (or any nation) was a nation of Christians, then God would fight her battles. America is not, nor has it ever been, a nation that was founded on Christian principles. From my observation, Former President Bush attempted to be the President first and then be a Christian. Some will argue that it has to be this way because we have separation of state and church. I say how can you expect to have God's protection when you do not put Him first. This is where the real problem comes into play. When these "waterboarding" questions get asked, many will try to balance between Christianity and the reality of our world. As Christians, that would make us lukewarm. We can never put the world's way before God's way. If America is not really a nation of God, then she is left to defend herself.
I have written a lot, but not really answered the question. That is because I still do not have all of the answers myself. What I do know is that there is never a time for it to be okay to sin. Bum makes the point that it may be a matter of conscience. The Bible tells us that eating meat is sinful if you think it is sin, and not sinful if you do not believe it to be sin. However, I just do not see acts of torture in the same category. These answers can only come through continued prayer and fasting.
I have a different take Fitt. There are many things that are the result of sin: death, dying, pain, suffering, killing, killing in self defense, etc. I put war in that category.
We cannot simply call ourselves Christians, and citizens of a certain country, then sit back and do nothing to defend the country. We can no more refuse to protect our citizens through armed conflict than we can disarm our law enforcement, stop maintaining the roads, eliminate firefighters, etc. In my view, there is nothing inconsistent about being a Christian and being a member of society, including contributing to the well-being of society.
It really isn't possible to hide in our houses and ask God to defend us. IMO there is always an action requirement on our part. Reminds me of my favorite Homer Simpson prayer: "Lord, if you don't want me to do this, please say absolutely nothing."
Much of this is indeed a matter of conscience. Some people think drinking alcohol is a sin. Some don't think it's appropriate to eat whatever you want. Some think you have to dress a certain, way, wear certain headgear, etc. I know some who think Christians should not serve in the military. I actually had a debate with a pastor who served as a chaplain in the military and believed any Christian who served should serve in a noncombat role. I told him he was no different than a grunt who pulls the trigger, because a Chaplain helps a soldier satisfy spiritual needs, which then makes the soldier a more effective killing machine. He disagreed.
But at the end of the day, this whole waterboarding thing is pretty silly, especially as some sort of religious litmus test.