No, I understand that you sound like the type of person who prefers to dispense with our legal system, have no problems with police absuing their authority and actually enjoy extra-judicial acts of violence.
Tell me, when the men in my neighborhood ran down a thief last year after he had stolen a bike from a local girl, were we wrong to be happy in the accomplishment,
Of course not. What a silly question.
including the bruising tackle the thief suffered at the end of the chase when we dragged him down to the pavement at the curb in the middle of an intersection?
Taking a suspect into custody is an accomplishment. Taking pleasure in the degree of physicality in doing so is not. It's closer to a pathology.
Was it wrong for us to be gleeful in watching him rightly suffer at our hands for the wrongs he did our neighborhood?
Yep.
Was I supposed to be tearful and sorrowful when a boy who mugged me at gunpoint was literally tossed 10 feet into the back of the paddywagon?
No, of course not.
Why?
See above.
Did his "human dignity" demand kid glove treatment?
Certainly not. Ignorant of the circumstances surrounding your scenario, I have no idea how he should have been treated and why a 10ft. toss was 'necessary'. Once a perp is hooked, there is precious little reason for doing so.