I understand your shock. Based on reading the whole thread, I have a few ideas that might help you work on the attraction.
I think you can get past the trust - he was protecting a very vulnerable side and perhaps he was trying to not do it anymore and was honest in his attempt. It sounds like he knew it wouldn't be acceptable to you. I see the biggest issue being attraction and he probably figured that would be an issue and hid it so as to not hurt you or expose himself to ridicule.
"Thinking" aloud here...
If he likes the feeling of restraint mentioned by another poster - and that could be what makes him feel safe (based on insecurities/bullying) or manly (bulging out of):
- do some role play like you are a cop busting him for something and he's trying to get out of the charge
- give a blow job through the hosiery, ripping it and freeing him toward the end
- would he like you to be more assertive in the bedroom?
- could you agree to incorporate his fetish a certain number of times per month if he ups the ante for you a few times a month by doing something super masculine like 'taking' you or talking dirty?
- can you look past the fact it's traditionally female garb and focus on his erection/excitement so that you feel excited about his hardness?
- can you ask him to do what he normally does alone to show you what excites him - perhaps in a mutual masturbation session?
If you can find any way to maintain attraction - not to him in women's underwear but HIM. His body, his maleness, regardless of what he has on - I think that might help.
Or lastly you could ask him to keep it strictly private, that you don't want to know that side of him exists, but frankly that probably won't work long-term.
I don't have any experience with this - I'm just drawing off of the other posters.