It's funny that you bring this up when you did, because last night I escorted Miguel to prison, and we then get ambushed by 8 smugglers. Since there's only one entrance point to the prison, I set my three men up to triangulate and concentrate their fire on the single doorway.
During the course of the battle, the smugglers threw three grenades at the prison, none of which cleared the wall. One exploded immediately in front of/slightly below the guard tower, another detonated right near the exterior entrance of the gate control booth, and the third sounded like it exploded right up against the base of the wall, where two guards were no more than 7 m. away.
One would expect the prison guards to start unleashing righteous lead on the smugglers assaulting their prison, right? Wrong!
Instead, they just kept on calmly doing their sentry duties. That is until I sent Pquito up top in the guard tower, he was easily 2 m. to the side of the guard, and every time he opened up on a smuggler, all of the prison personnel became hostile to my men, even though no one was directing rounds their direction!
When I exited the prison, I discovered that one of the guards by the gate control booth was bleeding out, and doubtless due to receiving shrapnel from a smuggler's frag.
I can understand why guards native to an area would have to be "immune" to the incoming rounds of enemies, so that it would prevent the Player from gaming the system by deliberately placing men immediately behind guards to use them as human shields and in the hopes of provoking them to align themselves to the Player's cause, but what happened last night was ridiculous. Two grenades should be more than enough to compel the sentries to respond.
Is there any way to make adjustments to the neutral armed AI that are more reasonable?