In my experimentations with Balschoiw's general method in arma, I find that to not work all that well.
In my experience, here's what happens if you try that in arma:
You spot a group of civies moving, let's say 200 meters away. You drop and call them out to your squad.
Even though you can clearly see that they are carrying arms and acting hostile, your group just doesn't notice this.
The freindly/neutral/hostile indication seems to only happen at say 100 meters or so. Until that distance, the AI just assumes that they belong to the side specified in their config.cpp.
This means that the AI will only open fire on that group of civies if directly orderd to or when the civies open fire first.
I suggest you look into madmedic's African Militia and either use the same concept he used to make some custom hostile civies of your own, or use his straight up.
Then combine that with setcaptive.