Were I so inclined, I would create and display contiguous to their protest and in massive font this quote by John Stewart Mill:
War is an ugly thing, but not the ugliest of things. The decayed and degraded state of moral and patriotic feeling which thinks that nothing is worth war is much worse. The person who has nothing for which he is willing to fight, nothing which is more important than his own personal safety, is a miserable creature and has no chance of being free unless made and kept so by the exertions of better men than himself.
There are other quips and catch phrases to compete with Mr Mill's perception which are heaved upon us by the leftists and the cowards addressing war, but true principles when in contrast to lies and distortions always remain victorious as considered by reasonable and sensible individuals