That does sound totally weird and I would be so freaked out by that reply. I would have expected any therapist to say something like : I understand how you might feel like not discussing this any further, but especially with the misunderstanding I feel like it would be helpful to examine this further and to repair the damage it might have done to you trusting me. However if you feel unable to discuss this at the moment, I will respect your choice and will wait until you bring this up again once you feel ready to do so. And instead of defending himself and reassuring you that he does understand what's going on - what about how it made you feel. I would have expected a bit of reassurance. I'm sorry that you felt ashamed and embarrassed. There is nothing for you to be ashamed of. I am so happy you trusted me enough to bring this into discussion and you are so brave for doing this... Etc some other kind of reassurance although I know some therapists would leave this until the next session rather than discussing via.emaild. and maybe some more analytic therapists wouldn't even go into this sort of reassuring but would want to analyse and understand your reaction further.

But as a fellow bulimia sufferer I can say to you ,- trust me.. there is nothing to be ashamed of. You are not gross. It's a horrible mental health illness and a very unfortunate and dysfunctional coping mechanism. But it's not your fault and it doesn't make you any less valuable or lovable than anyone else.