I fail to see how "they want war" is a good argument in favor of giving
them war. If war is what they want, isn't it better to find a way to keep them from getting it?
Sure, one can argue that there are situations where force is necessary to ensure the survival of your nation or its population. What's dangerous and self-destructive is jumping to the conclusion that that will always
be the case. That was the whole point of this novel. Earth and its allies had just come out of an inescapable war for survival. That was a case where a military response was necessary. But does it follow that the same response would be appropriate in a different context, in response to a different astropolitical environment and a different challenge? It's always dangerous to fight the last war, to assume that what you did in a previous case is the appropriate response in a new situation.
And as I've already said, there's no sense turning this into some ideological debate about the legitimacy of war in real life. This is a story about the history of the Federation, and we know that the Federation did not become a warlike military state -- that even though it was born out of war, it ended up going in a more peaceful direction. It's silly to argue about whether that "should" have happened; it's what did
happen, and the question is how and why.