So I just finished this mission and nobody was killed, stealing ammo from turrets in the village didn't helped actually, turrets were shooting even without ammo lol, drugging turrets didn't helped either. As someone suggested here, you will need to turn turret switch on or off and advance further.
It's 100% working but you will have to do it fast and you need at least 2 squad members otherwise it won't work:
1 -
(S) Here is our switch that activates turrets outside and deactivates inside. Position someone next to that switch, the other person needs to be in
(A) place.
2 - Hit the switch and run like hell from
(A) to
(B) and quickly hit switch again.
3 - In the red room you will have to take out those turrets
(C), the best method to do it is up close standing next to turret, hehe they can't hit shit when you stand next to them.
4 - Hit the switch again, run to
(D) and near the turret
(T), and hit quickly switch off.
Destroy turret or leave it, and now you can get the fusion battery and repeat the whole process on your way back,
it's the easiest way.
Hope it will help someone.