Absolutely not. That's why the parents belong in prison. They effectively killed their child the same as if they had let him play in traffic or handle a loaded gun. There are all kinds of hazards out there. Property owners have the responsibility to properly mark, enclose and warn others of them, but they don't have the responsibility of supervising their neighbors children. That same child could just as well have scaled a fence and drowned in a neighbors pool. Drowning deaths are far more common than fatal dog attacks, (more than 100 times as common).
The parents of the pit bulls? Just what have you been smoking?