Except it really isnt, good people will still fight wars of self-defense, wars to protect the innocent
And lawful good people, recognizing that wars will still happen, can reasonably sign onto something which they hope will limit the scale, atrocities, and death tolls of wars, even if they know they won't be stopped.
They might further work to abolish wars in general, but if someone wants to fight a war of conquest, etc, they'll fight a war, and the lawful good person would have to be ready for that, and recognize limiting wars is certainly better than not doing so.
But thats the secret, its all political.
The reasons things are the way they are usually has politics underneath, as well as the reasons people push to keep things that way.
Usually if you don't see the politics you either already agree with the underlying politics or need to look harder.
And generally its easier/more effective to deal with the root cause than simply try and address the symptoms.