Many of the dogs were used for protection by their owners. They were trained to only be controlled by their owners. These dogs are totally unapproachable, even if you wanted to just rescue them.
They are a huge danger to rescue workers. But, whenever all these volunteers that are willing to rescue these animals and care for them arrive, (must have had a flat tire along the way or something) they are welcome to try save that starving pittbull, shepard or Rottie chained up in somebodies yard.