War is indeed sinful.
The Civil War was sinful on both sides. But look at the atrocities on both sides. How can you call any of them moral. The Nazis were wrong and therefore we had to take the measures that we did. But I challenge anyone here to call the firebombing of Dresden moral. Come on, anyone? Is there an answer to this?
Jesus does allow us the right for self protection to a point. But only to a point. The high priest’s ear was restored because Jesus didn’t consider even His own death to be justification for that level of violence.
We may protect one’s self, but not aggressively pursue world domination, according to Scripture. Jesus admonishes us to allow our enemies to pluck our beards. I do not detect that except with derision amongst the fundamentalists. I quoted this recently on a post and had the post replied to with the general thought that I was a masochist and that I enjoyed being a martyr.
Tell that to your church.