Title says it all. Colonists with the "Kind" trait should get a mood debuff from shooting at hostiles who are currently in "fleeing" mode after being driven back during a raid/siege. Something like "They were running away, and I just kept mowing them down..." Maybe -5 for a few days.
An edit: If they're drafted and shooting at enemies when the enemies begin running away, "Kind" colonists should automatically stop shooting. They wouldn't become UNDRAFTED, they would simply disable the "Fire at Will" command. Manually re-toggling it and forcing them to shoot at a fleeing pawn would give the debuff.