My point was that while it is entirely possible for someone to hurt an armored police officer of today with a rock, rock throwing would be largely ineffective at driving back the police if they were allow to use force in return. Sure if you throw enough rocks at an unresisting foe, even if you weren't really causing any harm, eventually they would back off. Also the armor police use today is no where near as protective as armor was back in the middle ages. They usually have some sort of soft armor chest and back armor with a 8x12 hard or even soft ballastic plate in the center of their chest and back. Occasionally they have side armor protection. They also wear a helmet with face shield and maybe elbow and knee pads. This leave a whole hell of alot of soft tissue exposed, things like the neck, underarms, waist, groin, upper legs, lower legs, shoulders, upper arms, fore arms and even hands exposed to those rocks. The armor in Bannerlord doesn't leave that much exposed.
Speaking of Bannerlord, lets get back to it. The largest rock that someone would likely be carrying and throwing as a weapon would be maybe 1-2 lb and the size of a baseball. You could probably throw a rock this size maybe 20-30 mph (consider a baseball weight 5.5 ounces or 1/3 lb and most people can only throw one 60-70 mph). Against someone in padded armor like a gambeson, at hit might cause a bruise. Even chain which has very little rigidity and lacks protection against blunt force, at most you would get are bruises from rocks and you could probably take dozens if not hundreds of bruising hits before you were incapacitated or killed. Against any sort of rigid armor like say the lamellar armor widely depicted in Bannerlord, you would suffer no damage if hit by a rock.
If we are taking hits to the head, ok if you weren't wearing a helmet then yeah, sure a hit from a thrown rock could be lethal. Even if you were wearing a chain coif, a hit in the head from a rock could be lethal. However any sort of real helm, especially if it had face and jaw protection, would largely protect the wearing against lethal damage by a thrown rock. As someone who has been hit in the side of my helmeted head with a 6 ounce hockey hockey puck being cleared up the boards at probably 60-80 mph, I can say it will ring your bell a bit, but it doesn't actually hurt though I am sure if I had it happen 6-10 times in a short period of time, I could see myself suffering a concussion or something just due to the sheer repetition of hits but your not getting hit in the head by thrown rocks all that often in game.
Also, I guess you might be able to get some stagger effects hitting hard armor. Throw a 2 pound rock at a guy and hit him in the chest, his forward progress might be halted or he might have to take a step back. Hit him in the helmet, sure that will stop him up and if you caught him unbalanced, he might actually fall but getting staggered or even failing isn't any actual incapacitating damage.
Now lets talk looters. They aren't normally hitting you in the head, instead they are hitting you mostly in the body, arms or legs yet fully armored with a rigid armor and full helm, they can damage and kill you rather quickly. That is quite a bit of unrealism right there.