What I've doing in my current mission is I've created a small fenced off detention area to hold troublesome civilians. Then created a trigger the same size as the area and have it trigger every x amount of minutes/hours.
Then using something like
[getPos <triggername>, [side player], -10] call ALIVE_fnc_updateSectorHostility;
should slowly bring down the hostility of your detainees.
I haven't worked out whether I want to automatically release them or what yet, but I think it's a cool role play mechanic.