You know, I first came to this forum when I discovered my wife wanted to watch me masturbate. I had a real hangup with ever even admitting I masturbated. I saw questions similar to yours, so I decided to join just so I could share how my wife was successful in getting me to do that for her. That's actually why I chose my monniker.
If you're interested, my story is on this page: Do women like to watch men masturbate?
It's the only post on that page that I made so you can't miss it if you're interested.
Your husband's hangups may be much like mine. Mine went all the way back to school when masturbation was ridiculed, and the things like "Real men have women take care of their needs. If you don't have that, then you're a little jack-off." My hangup had nothing to do with fear of being homosexual like I hear some people say. For me, discovering how much my wife got turned on by watching it is what motivated me to get past my hangup, but as you can see if you read the story, it was still very difficult the first time I did it for her.
Now, it's not a problem. Now that she's gotten me past it, it's also not something she wants all the time. Like about 100 other items and kinks we have, it's something that just goes into the mix and gets done sometimes ... we're happy about that kind of mix, and I'm happy at the way it turns my wife on in the times when we do this.
Hopefully, you can find something helpful in my experience.