Re: Forget the kiddies
"The image of the bully as an empowered sadist does not reflect reality in my experience."
They do from my experience (both firsthand and through living next to a school for a number of years). There are two types of bullies. You describe the broken bully who bullies because he/she is bullied him/herself. The other type is the one I saw: the sadistic sociopath who gets off on bullying and has the connections to get away with it, such as being child to a prominent community figure or being genius enough to compromise grown-ups. The first type may balk if retaliated because he/she may not be used to the cornered mouse, though as you note if the bully is him/herself cornered, the result may well be escalation instead. As for the second type, they take getting away with it into consideration so will have plans in place in case of retaliation.
That said, something more sophisticated may also be lost on them, one because they're too full of violence to recognize anything else, the other because they're too smart for that. At some point, you may have to throw up your hands and realize you're dealing with a hopeless reject.