I guess maybe because I am Catholic (and Italian where wine is served w/all meals) I cannot fathom why one adult would ask another to refrain from having a beer. If it were me, I would have never even thought to ask this other person if it were o.k. if my husband had a beer or not. And I'm quite sure his reaction would be the same as your fiance's -- it would be a matter of principle moreso than actually having the beer. I personally could not be friends with people who required me to be a certain way in order to be their friend, but that is just me. If you really want to be a part of their church, I guess you should go and ask your fiance not to drink, otherwise I would just go and drink the beer without offering any explanation. IMO, you do not owe this woman a reason why you and your fiance, grown adults, enjoy a beer before the game. Most people do, its not a big deal to most people, and if its a problem for her then she doesn't have to drink one.