I was just closing before hitting the sack when I saw your post.
I don't know how well you know this couple, but if you enjoy their company and are good friends, then I would attend the wedding . Not attending might make it seem like you're prejudiced like the others. Would your hubby be attending with you?
If it was me I would do what I felt like doing if hubby is ok with it.
Some people will probably harass you over it, but then, there's always biggots waiting to jump on the soapbox.
I wouldn't have a problem with it myself, they deserve happiness as much as anyone else.
Take a break and enjoy yourself, you deserve it....no drinking though....lol.