Headkick in a boxing sparing session!? It's stories like the above few that really put me off of training. I don't like fighting regardless, I just don't have that mindset unless my temper goes (which is rare, I'm laid back as **** to say the least) but even then... I've literally been punched in the face, hard, and just smiled and walked away. Just didn't really phase me. I felt like that would infuriate them more than fighting back. A fight I probably would of lost in the process.
However I don't like the thought that someone's ego can literally mean a broken limb, purely because they wanted to show off a little bit. I know those cases are rare though, and don't happen everywhere. Gracie Barra gym near me is very well respected (Braulio Estima owns the gym and teaches there at times) so I would love to get into it at some point, so I can understand the intricacies a little bit better.
Oh yeah dude, I ****ed some guys arm up bad in rolling because I had him in a tight armbar and he wouldn't tap and i'm pretty sure if I didn't fracture it I did some nerve damage to him. That's why I always say to anyone i'm rolling with to just tap as soon as you feel real pressure on something there's no point of being a tough guy in training unless you legitimately are confident you are getting out of it.