Thanks for the reminder about relative Belli's between my ally and his victim, that had slipped my mind.
As for my end of the situation, I was doing all the "right" things, I just didn't have time to wait for the AI to get around to getting pissed off. Technically speaking though, THEY declared war upon me over an AWAC crossing into their airspace. I don't remember their belli towards me, but it could not have been much over 40%. I don't have a problem with the results, it just seemed a bit off that something as minor as a navigational error
would draw more political ire than a blatant invasion. ( I seem to recall a U.S. spy plane being shot down over Russia at a point in history when both country's belli levels were pretty high.) No worries, I'll start pissing them off earlier in the future.
As for insulting their mothers, that might actually be a nice diplomatic function to add, a way to diplomatically tell an AI where they can shove it. I mean, if a country wants to build up belligerence between themselves and a neighbor in real life, they don't have to spend gobs of money and time situating an army across the border (etc. etc.). They simply instruct their ambassador (insert equivalent) to announce something that pisses the neighbor off. Example: The Iraqis could tomorrow announce in Al- Jazira that their scientific studies had revealed that all Iranians descended from pigs. About 30 minutes later they would have all the Iranian belli they could possibly hope for.
I'm not sure how problematic this would be to add to the game.