I agree Yorkie... this is outside of your friends control... well, we all have choices but this would be rather huge to have to defy his religion and don't forget this also effects his bride-to-be and their family too. This could also be a church rule, as in they can't hold the wedding there if they let you be best man.

I understand how upsetting this is. I think you did the right thing by venting it here. I think don't hold it personally against your friend. Maybe you can talk to him and arrange for something special for you at the reception, like a toast or something. If not just help him enjoy his special day. Please also remember that this is a time for him when he is being pulled in a lot of different directions and making a lot of compromises just dealing with his family and her family... so find a balance to not stress him out even more. I'm hoping that by the time the wedding comes you can find some peace with this so that you are able to enjoy yourself that day too. Eat lots of cake!