IMO, knowing that his clients would be there and given that any of them might have transference issues (you were brave enough to share, some others might not have been at that point to be able to), it wasn't appropriate for him to have his partner there. I don't think that your email was out of line and perhaps after self-reflection he might come to the conclusion that he made a mistake. How he handles this situation will tell you a lot about how he is as a T. I really respect Ts who are able to admit mistakes and apologize. Those who never admit they are wrong or even willing to admit to clients that they have done self-reflection are not effective to me. Modeling is an important thing for my therapy given my parents who never admitted they were wrong, a bad habit that I picked up and am re-learning through good models like my current T. If he does admit responsibility, it will still need some working through, which will be hard on your part. Good luck!