Laurie posted this one. It's about school teachers, but a lot of what it says applies to coaching combat sports, martial arts, or self-defense. Some of it is startlingly obvious. Some of it just articulates things I think I already knew.
The "teacher as social worker" angle is interesting. I've been compared to a therapist by clients on numerous occasions. The psycho-social aspects of violence, and how people deal with it, are slowly becoming more interesting to me than the physical aspects (though those are still fun).
Anyway, go have a read.