Unfortunately, his Shihan has passed away recently. And that was the only person he would listen to...
His previous deshi is quite open about it with the other students. But he never acknowledges his mistakes and never listens to advice given by people that are younger than him. It absolutely pointless to argue with him or rationalize, or present a different point of view. I've come to believe that people don't change because someone told them to. They only change if they want to change, and this man is most resistant to change.
I don't know... I could write to the federation, but I don't want to be a bitch and cause problems for his dojo. "How people treat you is their karma, how you react is yours". Besides, who will they listen to? A college kid or an old, respectable Sensei?
You might want to consider that this shihan would be the person most likely to back/protect him. The head of the federation would listen VERY CAREFULLY to you and the previous deshi describe the pattern that you two had been subjected to. There is a lot of information and concern in our community about teacher abuses lately. The timing could not be better to raise this issue with the federation. Saying that you would "be a bitch" or "cause problems" is simply part of the unhealthy consequences of what you went through. The previous deshi tried to warn you and that did not work. Maybe it is time that you and the previous deshi do something a little more assertive to stop this unhealthy pattern. I am sure that the next potential victim of his "mentoring" will thank you in advance.