Re: dojo head bans students from training with another teacher (ex student)
I can see an instructor kicking a student out for lack of commitment. I can see an instructor kicking a student out because he did not like him. I can even see an instructor refusing to train a student because of his goals.
However, if I were to train at a school where the instructor felt it was his job to tell me what to do with the time I was not training with him, I would leave. I don't care if it was O'Sensei himself. I'd tell him sorry, but he is not the instructor I'm paying for.
When I join a school, I make a commitment to follow a program. That program might be 3 nights a week, it might be 1 Saturday a week, but the program is set. If I deviate from that program I expect to be called out on it. However, those other nights are none of the instructors business. That said however, if the instructor wants to make the rule, then it is your job to weigh the decision to stay with him. If you find the rule acceptable, then stay with him, it is your dime. Just remember, as much as he is doing you a favor by teaching you, you are doing him a favor by being his student. He is not in control, not a master of you, it is a mutual agreement. I'd suspect that if all those students told him they were leaving because of his decision that he would have to either reconsider or learn a life lesson that his word is not all powerful. However such a protest would cause strain in the school, and thus it would be better just to simply leave, the act of just mentioning you might want to leave has probably bruised his ego and will cause him to regard you a less a person.
I speak as a person who had to make this decision twice. One instructor realized that we could still be friends and my cross training was not personal, the other did not. My aikido instructor asked me to choose between aikido or judo/bjj. Forced to make a choice, I picked judo/bjj. My judo instructor was threatened by bjj and asked me to make a choice between his judo club, or my bjj club. I picked bjj then found a new judo coach. Luckly my aikido instructor realized that there was nothing personal in my desire to train bjj, and now I come by to train with them and we are all good friends. I think I add as much to their training as they add to mine. My old judo coach will never speak to me again. I'm a bjj thug now.
I however still think a good hard fast rule when being asked to make an US or THEM decision is to always go with the THEM. People who ask are usually doing it for their own selfish reasons. I just hope the day never comes where both sides are asking me to choose.