well, as it stands globlins find everything acceptable/p_m, so they won't attack another civ for any ethical reason, as the ethics tags so far as i can see are on a negative scale, if there are some on a positive scale, and goblins seem to be missing a sieger tag aaaand...
*Although, pretending to think about it, it probably has alot to do with goblins having little or no interest in the dwellings of other races, dark fortress is the only one they [...]
As ethics looks like it's purely for worldgen interaction, and worldgen interaction then sets civ vs civ stances, and you're out to be teh evilz, just set your entity to like all sites, and find everything acceptable, and everybodyelse to like just their own site, and find everything unthinkable. well, except kobolds i guess. Sounds of the comments so far is that additional civ entities are possible, so.. if they aren't, modding the kobolds out would probably be more interesting tan modding the goblins out..
Deon, I think it lists civs you're at war with with a red - - - - - - when you tab to them. I'll assume that when you go to that screen it's checking the civ of the race that you'd be trading with, rather than the race as a whole, which still makes sense, and obviously [if it's not bugged] a civ you're at war with would send an attacking force rather tha a caravan.