I think that the evil races were about as neutral as everyone else. They were wronged at one point or another by one of the other races (Whether they were or not has been forgotten), and they passed the knowledge to their children, and as this was passed through the generations, a seething hatred eventually began to encompass everything.
Their once simple grudge eventually evolved into something similar to the belief that they were wronged, and that they must destroy those who wronged them. This makes them into the bitter, hateful things that they are seen as, though they think their task is true and righteous.
No one thinks that what they do is wrong, and I don't believe that the goblins, orcs, and kobolds would be any different. They are simply fed and raised with the knowledge that they hate something, and that they must do whatever they can to destroy it. The same thing happens quite often even amongst us humans, and for things as simple as nationality and skin tone.
(This also means that there can be those who separate from their brethren and are relatively friendly, though I imagine these would be rare in a world where no stray thought is tolerated and everyone would kill them just for being what they are.)
Most of the time, however, you'll see the "evil" races as natural (Or unnatural) born psychopaths. It's simple, but it does make for a convenient enemy, especially when you don't want to worry about whether what you're killing might just be some poor ol' sap that would rather be shoving lemons into his eyes. It takes a lot of the bite out of war.
Not that this is a bad thing: I have to say, that for such a bloody game, Dwarf Fortress does spare us the decision of whether or not to kill something. So while I'm all for other races having complex morals and alignments, I understand the need for something you can shoot and not bother asking questions. Since Dwarven society is so complex, you need something you can beat up without feeling bad about it. Stress relief, and all.
Hm. It seems I rather rambled on a bit about that. Sorry.
Interesting website, though.
[ March 16, 2008: Message edited by: Dreamer ]