Re: What to do ?
Like Lynn, I am a licensed psychologist and Aikido instructor. I cannot understand what the psychologist meant by 100% responsible. That sounds like a strange statement for a psychologist to make. Lynn's point that a dojo is not a therapeutic environment is one that all dojos should adhere to.
At my hombu dojo in NYC, we had mentally disturbed people training at our dojo (one called herself Steven Seagal's psychic wife!). A psychiatrist and myself were always talking about how wrong it was to allow actively psychotic people to be training. When I had the "pleasure" of serving as president of that dojo, I allowed one incident to be the basis for instituting the policy of not allowing seriously mentally ill people to be training. It was disruptive to the other students and the potential for the unexpected also kept people on edge.
Ron's advice was sound! If an act of sexual abuse happened, then it should be investigated. The head of the dojo should be made aware and that person should act appropriately by expelling anybody who intentionally abuses another member. The dojo atmosphere requires a great deal of trust in each other. I cannot imagine how that can be fostered in this situation.
If the head of the school does not do the right thing, I believe that you should seek training elsewhere.