All Spirited creatures can be reasoned with. I suspect the assortment of people you met were the Vanguard of the army: shock-troops and lancers. They are under orders and, of course, are unable to make decisions on behalf of the empire or the army. Armies would cease to function if their privates started bartering or entreating with the enemy.
I do not suggest this isn't a dire threat, nor that these people are not conquerors without qualm or mercy - just that, unless they are elementals or some other Spiritless construct, they do have a reasoning mentality which can be approached. Dismissing them, out of hand, as abominiations will only ensure more death, as opposed to opening the possibility of peace.
Master Dramthin Hartsboon
Keeper of the Tainted Grove