Ok here is the thing everyone is hung up on RPG's and AT-4's only purpose is for stopping tanks and/or armored vehicles. The reality of this is that these weapons are used against infantry all the time.
For instance how many war movies have seen were two guys are sitting in a firehole and someone yells RPG... boom they are all dead. WTF the enemy didn't use it on a vehicle OMG I am gonna raise the bull shit flag, give them boys back there lives. I don't think it works like that ask anyone who has served in the military or is serving in the military it just doesn't happen like that. MaCoo that is a movie yeah and this is a video game.
People need to do there research not a single one of us know the intent of the programmers for this game. Besides they are trying to make a video game as close to reality as they can and still make it playable.
I did the research for you and when in doubt wiki it.. http://en.wikipedia.org/wiki/Rocket_propelled_grenade
Warheads
The HE (high explosive) warhead is a general-purpose explosive warhead for use against unarmored targets such as infantry, unarmored wheeled vehicles, and fixed positions. The HE warhead detonates upon impact. The warhead case and charge generate a moderate amount of fragmentation, which can pass through many obstacles without stopping.
Unarmored targets such as infantry -> someone trying to run across the map and avoid a sniper shot but not my RPG. ;D
Unarmored wheeled vehicles -> terrorist trucks from socom 3 and CA... Still died from my RPG...
Fixed positions -> someone camping a corner and using 3rd person vision to see further then they really could and popping out to kill a enemy target... unless it is me and then you get a rocket up your ass..
FAIR IS FAIR... don't debate the realism of a game when you obviously wouldn't pop out from behind a wall and drop someone with a head shot with one shot, again all the time your using the 3rd person vision of the video game.