Well considering building up fully costs well over 100 million in resources for anyone over 14 cities, not counting the lost income from upkeep, how are your members going to like it, when either
A. Arrgh wipes their military, setting back their stockpile and wasting 100 million (just to get a point across I used 100 million, it can be far more or less)
B. They don't even get to declare a war, they waste weeks of income and eventually waste 1/4 the resources they used building up.
In the end, what does a mass war against Arrgh accomplish? Arrgh has nothing to lose, it gives them even more opportunity to raid and steal your own resources.