I like the thoughts I see. And It's not that dwarves don't like killing neutrals. If I recall right it needs to be sanctioned (official order issued by the fortress leader/ civ monarch,) have no ramifications (animalfolk I'd imagine) or otherwise in self defense (berserking elven/human traders for example if they're considered neutrals.)
Otherwise more empathetic dwarves may be disturbed by it while more bloodthirsty/isolationist dwarves would enjoy it. Something like
"Upset when the leadership killed peaceful traders without due cause."
with no mayor/baron+ present or if the mayor/baron+ is also one of the soldiers who killed said merchants for those who would care about others. These individuals could also get a good thought like "Was pleased to hear -insertracehere- have become become fortress citizens recently" for multirace forts if they're ver implemented.
And "Was pleased with the leadership enforcing isolation." or something to that effect for those who are more violent oriented/favor isolation from percieved "lesser" races. If the above mentioned multiracial forts are ever implemented, this could aslo add an unpleasent "Was angered/annoyed/disturbed by a/an -insertracehere- being inducted into the fortress recently."
Sorry bout the race thing. Couldn't resist
"Happy that she got a share of the loot from the raided caravan."
"Has been yelled at by the Liason for law-breaking"
"Is sad to be confined for un-lawful orders"
"Enraged that leadership has begun a war with a beloved creature"
"Happy that leadership has begun a war with a hated creature"
And these. Though the liason and confinment thing would assume military actions override leadership roles of nobles/mayors or if they take part the killings are considered unsactioned.