Peace
I'm all for peace. And I mean, not only the good peace between free men who recognize and respect each other's freedom. No, I also mean the peace of surrendering to the (least) oppressor ( cleverly).
Yet in the end, someone somewhere has to fight, and it will be much better if bad guys don't win, which will require that they won't have a monopoly on violence. A universal argument that good guys should never fight is precisely an argument to give the bad guys an unlimited monopoly on violence, from which they will achieve total, utter victory. (As a moderating factor, however, rivalry between bad guys works against such monopoly.) Beside, if it is universal, an argument against fighting will not be just an argument against war, but also against any kind of police: if all baddies are always to be let do, that includes small baddies as well as big ones.
So there is the practical question of when to fight, and when not to. And relatedly and most importantly, whom to fight and whom to ally with. There are cases when the benefits of some fighting combination overwhelm the costs, and cases where it is the other way around. When the baddies are very small and weak and the good guys have clear supremacy, the baddies surrender when discovered, and the operation is called a police arrest, to be followed by whatever conviction the winning side may choose. When the baddies are very big and strong and the good guys are clearly subdued, the good guys would be foolish to fight, and can but hide amongst numbers, run away, and/or play the baddies against each other. In between, there is a point where the contenders have diverse degree of good and evil, where the victor is not obvious, where risk and degree of oppression is not certain, where the consequences of accepting, rejecting, proposing or breaking an alliance are unpredictable, and one may have to make one's mind and pick or not pick a fight on either side.
The saying goes that a bad peace is better than a good war; it's a lie. We saw above that sometimes, war is clearly advantageous. But most importantly, peace is not always an option. A horribly slow war where the oppressor crushes the victim to certain death with an extremely inefficient weapon is war no less if the victim chooses not to fight back. The SS or KGBist that keeps you alive in a work camp rather than executes you or walks you to death is your mortal enemy no less because he vows you to slow death rather than fast death. Your monopoly government is no less your enemy because it asks you for money at known regular dates rather than ambush you by surprise on the road.
Unilateral murder, robbery, rape, fraud, torture, enslavement, taxation, abduction and sequestration, and threats thereof are no peace just because you surrender every time. Don't let yourself be fooled. Passive victimization is not peace. It takes two to make peace. It takes only one aggressive party to make war.
And so, we often only have the choice which war we'll have. And because the bad guys always threaten to aggress helpless victims, the only peace that is achievable isn't just any bad peace, it's an armed peace.