I noticed something else recently regarding dwarven preferences; tweaking world generation parameters can have an affect on what kinds of things your dwarves like. How neat!
I generated a world with significantly higher evil and savagery overall, along with way too many titans, megabeasts, curses, and evil weather. Out of my first 16 dwarves, 8 had an evil favorite creature (three loved Bogeymen, the rest were fond of Ribbon Worm Fiends, Green Devourers, Hags Of Evil, Horned Horrors, and Monsters Of The Night, respectively). One had a savage favorite (Mosquito Men), and the rest either had no creature preference or were the normal geese, reindeer, and so forth. That's much, much higher than the usually observed rate of preferring evil creatures and things.
Incidentally, there was also a higher incidence of preferring plants, food, and drink from evil/savage biome crops (whip vine/silver barb), as well as general trends in the bone/leather favorites too.
I've also noticed that none of my immigrants so far have had pre-existing kill lists at all. It's very early in the game, however, so this may not really be a trend. It just makes me think that I inadvertently made a world that has been ruthlessly kicking everyone's ass before I even showed up, haha.
Anyhoo, I suppose this is all related to - as AutomataKittay pointed out upthread - dwarves developing preferences for things they've encountered. Apparently instead of running in fear the dwarves in my world think, "Oooh, neat, look at the tentacles on that one!"
This game is fascinating.