Generally, this post is the suggestion to modify plugin and stop NPCs from targeting the drone. Because players can abuse the drone by making helicopter to attack other players/buildings/etc.
But in case @k1lly0u will never made this change, here is how you can do it yourself:
find the following line in plugin code:

        private void Unload()​

Add the following code ABOVE that line:

        private object CanBeTargeted(BasePlayer player, MonoBehaviour behaviour)
        {
            for (int i = 0; i < DroneController._allDroneControllers.Count; i++)
            {
                DroneController droneController = DroneController._allDroneControllers[i];

                if (droneController.Controller.userID == player.userID)
                {
                    return false;
                }
            }
            return null;
        }

        private object CanBradleyApcTarget(BradleyAPC apc, BasePlayer player)
        {
            for (int i = 0; i < DroneController._allDroneControllers.Count; i++)
            {
                DroneController droneController = DroneController._allDroneControllers[i];

                if (droneController.Controller.userID == player.userID)
                {
                    return false;
                }
            }
            return null;
        }

        private object CanHelicopterTarget(PatrolHelicopterAI heli, BasePlayer player)
        {
            for (int i = 0; i < DroneController._allDroneControllers.Count; i++)
            {
                DroneController droneController = DroneController._allDroneControllers[i];

                if (droneController.Controller.userID == player.userID)
                {
                    return false;
                }
            }
            return null;
        }