A few points I would like to add, since I started the topic:
1) I agree, pacifism does not equal good. However, IMO, neither does unprovoked agression. As you say, good and evil should be clear - and it appears to me they are not.
2) The issue is not "predictability". If you want pure unpredictability, you can get it by rolling the dice with the other races at the beginning. The issue is consistency. "Good" races shouldn't attack each other without good reason. Example, in two of my games, the Alterians attacked me unprovoked, merely because my military was weaker than theirs. That's not the action of a "good" race to me. If they attack me, it should be for a reason. I do like the example given where if I am trying to exert influence in their zone, that it lead to war. There are probably other rational scenarios we could come up with for a "good" race to declare war.
PS, don't know if you can do this with spying, but it would be cool if you could "frame" other civs - this would be a legitimate cause of war in a sense.
3) As said previously, good doesn't mean wimpiness. If I attack a good AI, I have no problem with them wiping the map with me and conquering all of my systems to eliminate my threat. But I think they should have a good rational reason to launch an unprovoked attack - especially on a good or neutral race. Or like someone suggested, a substantial morale penalty. I don't think there should be a penalty for attacking an evil race though or vice versa - that's just what good and evil empires do
4) Is there a morale impact to declaring war, or having it declared upon you? Is there a morale impact to winning or losing? I think both of these should be considered.
5) The US and UK have not had numerous wars - just two - a war of independence and a subsequent war 30 years after independence. All other disagreements - and there have been a number of very serious ones - were worked out through negotiation - not war.
6) I'm not trying to take advantage of the AI here either, as someone claimed. Without a good reason for declaring war, I think a) my civ should take a heavy morale hit with related election of govt problems

suffer a much greater possibility of civil dissent - maybe lower productivity or lower money generated c) greater possibilty of some sort of rebellion. It would be cool to get a popup stating a "March for Peace" was held on my capital planet

And these should increase the longer the war goes on. And should increase even more every time I do this. This would keep me from a cycle of declaring war, taking a planet, making peace, and doing it all over again - without running the risk of substantial problems/penalties. This would really take the game to a different level - Civ tried this with making it harder for demos to wage war - but it never really functioned in terms of good vs. evil actions. I think GalCiv can do more here.
7) But I am not just talking about the AI here. Another point I was making is what makes me evil. I think if I declare war for no or wrong reasons, then my empire should tilt towards evil. That should also have a greater impact than my attitude towards sea creatures, lost starships, deserted alien cities, etc. These seem to me to be small exceptions to what should have greater impacts - foreign and domestic policy.
I've already written about foreign policy, but with respect to internal policies, democracies should rate higher good, and imperial govt should rate more evil. I probably could think of others internal factors to consider if I gave it enough time.
I guess right now my point is this: the evil vs. good thing in the game is a great idea - no other game has it - but I think it's implementation is weak, and based upon relatively trivial factors/issues, while ignoring more important issues that determine "good" vs. "evil". At least how history often sees it, IMO.
Grifman