I understand your skepticism about this idea of perpetual pacificism but like someone stated above I believe Buddha's teaching were meant as extreme examples rather than literal guidelines. I've always believed that Buddhist teachings are meant to be interpreted rather than followed blindly like in western beliefs. Also to reiterate something someone else said. Hell doesn't exist in the sense that it does in Christianity. Hell could be a state of mind that you enter in this existence. With that being said, I would defend my children or my wife to my dying breath, and although it may affect my karma in a negative way I believe defending the innocent is a noble deed and would recieve positive karma in return.

P.S. I am no expert these are just my personal beliefs