“So, turn the other cheek, but you only have two cheeks, and walk the extra mile, but only one extra mile. Peace on earth to all men of good will, but Old Testament solutions are applicable to men of bad will. Christianity is not a suicide pact.”
Jim, “The Logos,” Jim’s Blog (May 6, 2023)
Christianity is not a suicide pact unless we make it a suicide pact, in which case it is a suicide pact and we all die. We make Christianity a suicide pact when we imagine that a Christian has overcome the world and its tribulations, whereas the truth is that Christ overcame the world and we Christians remains in it.
In the world ye shall have tribulation: but be of good cheer; I have overcome the world (John 13:33).
This means that a Christian remains finite and therefore exhaustible. A Christian should turn the other cheek, but he does not have an infinite store of honor to lose and can survive only so much insult and slander. He must not be “hasty in his spirit to be angry,” but neither should he be without a spirit to be angry. A Christian should show forbearance and longsuffering but not servility. He was not put on earth to be the drudge of every bossy bully and bitch who has a mind to give him orders. And a Christian must never forget that Christ expressly denied that he had come to “send peace on earth.”
What this comes down to is the fact every Christian “shall have tribulations,” which is to say enemies. Thus he needs friends. And if he treats his enemies as friends, and worse than that his friends as enemies, he has made his faith a suicide pact in which everyone dies..
The Orthosphere 
I agree and offer another angle.
True Christianity seems to end in two places when exposed to intense evil: the martyr and the warrior. They are not mutually exclusive. One can flow into the other. They balance.
Without the warrior, martyrdom-only can become a suicide death cult. The warrior – willing to scale force righteously for G-d under the virtues guided by charity of what he protects – stops this.
Without the willing and righteous self sanctifying martyr dying to Christ in love and devotion, the warrior culture devolves into a killing death cult.
Under Christ, both limit the worst and enhance the best in the other.
I think a martyr may be just a cornered warrior. I think a true martyr was offered his life in exchange for apostasy or blasphemy, but refused and thus chose death over spiritual surrender. I also think you are right that violence is mere brutality when it is not somehow sanctified.
Modern Christianity, suicide pact version, is a strange amalgamation of ancient heresies. The exact mixture and portions of each should probably be understand so that future generations of Christians can be on guard against it.
I am not learned enough to do the necessary work, but merely am recognizing its necessity.
“Watching other people making friends, everywhere, as a dog makes friends. I mark the manner of these canine courtesies and think, here comes, thank Heaven, another enemy!”
— Edmond Rostand (Cyrano de Bergerac)
Not *quite* in line with your post, but your words brought this passage to mind.