Savn, there is no good(for all involved)answer to your question. Someone is going to get hurt feelings and perhaps enduring emotional pain from the event no matter which way you go. It has already occurred to some extent, but forced action on either party's part can fester and grow as the days pass and even become years. It is easy to see that considering your friendship with him, the gay person thought you wouldn't mind, but he should have asked. I'm going to stick my neck out and say that he is in the best position to resolve the matter with fewer hurt feelings by gracefully backing out and taking another part in the ceremony. This with a smile on his face. It would show love for a friend by not making him act against his own religion and allowing less conflict between parents and their child for this oft long remembered event. Best that this action by him would come unrequested, but as a peacemaking gesture. However, that does not answer your question. Forced to the wall, I just couldn't miss my daughter's wedding. I would smile, and walk down the aisle with her. I'd pray to the Lord that I made the right decision, and to be forgiven for any wrong.