Respecting a spouse's feelings

Just recently went through a horrendous time that started out with what would seem as a somewhat inocuous, but hurtful, situation.  Husband, who was diagnosed with ADHD several months ago, sent me an email that included a poem he had decided to write to a young female coworker, who had a miscarriage late in pregnancy.  There's a little more history to this than I present, but nothing previous to this was hugely inappropriate.  My first gut instinct reading this email that explained how he was being so open to me and how he realizes that it MAY appear to others as inappropriate, was anger and pain.  I had already started feeling uncomfortable about this person because my husband had said he admires her, she's a "good friend", he likes to talk to her, etc. (more here, but doesn't change the main point of the story).  He said that he knows she enjoys poems and he purposefully wanted to do something personal and that's why he didn't just send a general letter of condolence.  He addressed to just her and didn't include her husband. His explanation was because she's his coworker, not her husband.  I thought it was highly inappropriate to be sending a very personal poem to a married female coworker and to address it just to her.  He didn't see it that way.  After weeks of arguing, crying, therapy, he has finally agreed to only have a professional relationship with this person.  That is AFTER weeks of arguing, crying (on my part) and therapy.  I just couldn't understand why he refused to give up this friendship if I thought it was hurting our marriage.  I absolutely do not think they're having an affair- emotional or physcial; although he admits to having an emotional attachment to this person because she gives him a lot of admiration (that I don't give enough of; but with the ADHD issue, you can probably see how hard it is to do sometimes).  I take responsibility for not meeting his needs for admiration, but when he saw me lose 10 lbs from this episode and the extreme hurt I was feeling due to his refusal to give up the friendship; he still felt that the "friendship" wasn't the issue, so he's not going to give it up.  It made me even more convinced that the friendship meant more to him than either he realized or I realized.  I do have some trust issues (based on my childhood and not a lot from anything my husband has done since he's been faithful for our entire long marriage), but I can't imagine that I could stand by and watch my husband go through that kind of pain and not do what I could to alleviate it if it was in my power NO MATTER THE REASON.  I said he didn't give up the friendship because it was my issue with trust; but now I trust him even less.  I don't trust that he'll be the one to protect me.  I believe I can count on him as long as he thinks it's reasonable and it doesn't go against any of his principles.  Was it wrong of me to expect my husband to not have anything beyond a professional relationship with a female coworker?  This story is very complicated and there's a lot more to it than I can explain, but I know he still believes that he shouldn't have to give up this frienship even though he has agreed to.  It hurts me to know that he values this friendship that much even though he denies that's the case.  Not sure how to ever get beyond the hurt.  I know I should feel lucky that my husband has been faithful and he does try so hard to please me (except in this instance).  I want to get over the hurt.  Part of the ADHD thing is that they so strongly believe that they are right.  I don't think he'll EVER feel that what he did was wrong.  He believes that he's just giving in to an irrational feeling and he just doesn't want to fight about it anymore and wants to get past it.  He doesn't believe he should have to give up any friendship he believes is innocent no matter the effect on me.