So in CIV:BE, they added a system where the AI will complain about your actions and ask you to agree to change them instead of just engaging in a hate war out of nowhere. The problem with this is that it exposes just how insane the AI is. For example, in a recent game, I built a city on the opposite side of my civilization from an AI, in a tiny strip of coast that wasn't claimed by my capital, then they complained that I was settling in lands they considered to be theirs. Really? Apparently, any tile within 30 hexes of your borders, you consider to be yours, even if there is an entire civilization between you and it. Of course, any time you ask an AI player to not settle near you, they always decline unless you hold favors they owe you against them, but if you decline just once, they'll remember it forever as a slight against them.

Then there's the matter of the AI proposing deals, then rejecting them after you accept them without modification, not to mention generally not being reasonable when they need something, such as passage through your territory (Because how is the good will gesture of mutual open borders not reasonable?)

And let's not even bother with the "My economy is entirely dependant on yours, and I will actually admit (yes, it's part of the war message)that you'll probably defeat me, but we must go to war" thing.