11 or 12 years ago, in our dojo a visiting black belt (although I don't know if he announced himself as such) was being pretty ruff. He stopped a throw on my buddy short (instead of following through so he could roll out properly) and hammered my friend, shoulder first, into the mat.
Later that evening after practice, my buddy came over to my house to chat, mentioning this guy's bad attitude. When he pulled off his jacket my eyes almost popped out of my head -- his shoulder was hanging around the bicep level. My buddy said, "ya, it really hurts". No kidding - his collarbone was broken. A few weeks later we learned the black belt was from the Ki Society dojo at our local University, and he was out to show people that Ki Society Aikido wasn't just a dance.
Well my buddy had his arm taped to his body for months and couldn't even shower properly let alone do Aikido -- all because someone was out to coddle their ego. While maybe he didn't "intend" to break my buddy's collarbone, he did intend to be ruff and mean and that's what happens when your ruff and mean.