Another POD to EllenS.
We see so many posts about people wondering what it "means" for them to attend a wedding when they don't approve of the match, too.
It doesn't mean ANYTHING other than that you are there to share an important day in the life of someone you care about. It doesn't mean you endorse everything or even anything that the officiant or anyone else says. It doesn't mean that you approve of the marriage. It doesn't mean anything at all about us guests -- the wedding is not about us. Attendance does not equal endorsement. No one is thinking about us or our opinions anyway. It is possible to be offended and, as others have put it, just let it roll off you when it is in a context like this. I cringe when I hear a wedding with the "submission" parts, too, but no one is asking me to sign an endorsement, you know. It's simply not about me.
The only reason I could condone walking out is if, as others have said, you simply cannot control yourself for some very unusual reason and would make a bigger scene by staying. But rules of etiquette are not built around such exceptional cases. Walking out of a wedding is a VERY BIG DEAL. I wouldn't do it unless I were sick and about to vomit, no matter how offended I was -- and I have been, very -- at weddings. And even then, I would do it absolutely discreetly.
I wouldn't tell anyone else later, either. I might totally hate what that officiant says, but it is rude to trash your friend's wedding ceremony, let alone to insult other people's expressions of their own religions in their own churches.
Ditto funerals. I'd never heard of funerals where there is no eulogy, only a fire and brimstone evangelical sermon, so I was taken by surprise years ago when I went to our office manager's mother's funeral that was like that. The other law partner and I were -- very conspicuously -- the only Jews in the room, and I don't think that it was our imagination that the minister looked directly at us almost the whole time. Our poor friend was so embarrassed and apologized to us afterward. It was indeed very uncomfortable, but we assured her that it wasn't, at all. Of course we hated every second of it, but we were able to remember that this funeral was not about us and our feelings, it was about her and her feelings.
The funeral Figgie described might be where I would draw the line! Wow. I mean, that guy was making people DO something they didn't want to do while he was insulting them. (I wouldn't, say, take communion or stand up and say I accept Jesus as my savior or that there is no god but Allah no matter how politely I was asked.)
But simply hearing something I disagree with, no matter how strongly, and even being quite offended, are to me insufficient grounds for boycotting or walking out of someone's wedding. I accepted the invitation, and this is what they were inviting me to, whether I like it or not. If you are truly so hypersensitive that you simply can't bear it, then decline the invitation the same as you would have to do for any other handicap.