That's why we call them "donorcycles."

Hmmm, Pit bull terriers. I've raised them & been attacked by them. "Real" breeders of pit fighting dogs only breed game dogs. If a dog won't scratch or turns away during a roll, they're deemed "not game", usually destroyed and definitley not bred. Likewise "people mean" dogs are destroyed. Kinda ...

What If the border protection was left to each individual state? State border patrol instead of Federal. How about it? It would certainly help to downsize the federal government and probably help each state's economy.

To answer "when to risk injury or damage?" ...DON'T. A body can be coaxed not forced to adapt. "Train don't strain." Rolling barbells on the shins, for me is out. Shin kicks to a heavy bag work. Parts of the body, mainly the hands can be toughened up quite a bit. I've never seen calloses on anyones ...

Calibre Press sells a book titled 'Verbal Judo"

Simply going barehanded/footed on your canvas heavy bag is one. Start easy but you can develop callouses on your fist etc. For grip, wrist strength, toughness and reflex training, try tossing different sized pipes and boards back and forth between partners or simply do it alone by tossing them up ...