I assume the current implementation is something like "if a single faction member of trade caravan is hit for more than 5 times, set them to hostile".
Which means you can
1) Shoot their muffalos *just a bit* and hope they bleed out without consequences for the colony.
2) with a very skilled shooter oneshot a member of the caravan without consequences.
Especially 2) seems a bit weird. I think they should attack if one of their members is killed by the colony.
Stay away from exlpotes, please don't try this until it gets fixed because it will get boring!
Maybe we should distinguish between accidental friendly-fire and a deliberate one. And make it so if the player intentionally targets a trader then one shot is enough to anger the faction, or at least make them leave the map.
I am sure I could exploit the "target intentionally" thing by somehow attack nearby wall with minigun or target a nearby squirrel with mortar :D.
Sounds like a good compromise though, especially making them flee earlier if they somehow end up in (friendly)fire.
It's the whole faction you're angering, and yes you can shoot them a few times before they attack. Working as designed. Thanks for the report.