[Squirrelloid]

I'm not sure I'd say I'd dislike someone who is evasive and canny when i'm playing as an opponent in a war game. I'd probably respect them for it. Misdirection is fundamental to the art of war, and diplomacy is just war by other means. Consider the words of Sun Tzu:

"All warfare is based on deception."
"Let your plans be dark and impenetrable as night, and when you move, fall like a thunderbolt."
"Be extremely subtle even to the point of formlessness. Be extremely mysterious even to the point of soundlessness. Thereby you can be the director of the opponent's fate."

I find it hard to dislike someone for conducting themselves skillfully in a war game. Of course, if they are really good at it, you may know they were non-committal, but you won't know what their aims are.

Re: Civilizations
Its other people who are making judgements about diplomacy, and they are making them based on exactly what they should be making them on: relative advantage, future prediction/projection, and self interest. That you think troop morale should suffer when attacking a weaker foe is mind-boggling.

Re:Standard rules for diplomacy
Standard diplomacy is Machiavellian - ie, only what the game engine enforces, which is nothing. There is no other standard. Machiavellian just means caveat emptor, not that you can expect everyone to lie.