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.