Whilst your motives seem genuine, your views seem a bit....distorted. It would be natural to have a concern for your partners welfare, but it seems your concerns are more down to something else. It sounds like (and if this is all wrong I apologise as I do not know your or your fiancee) you either have some issues yourself that you need to sort out, or if you are always going to feel like that you should find someone who has the same views on those things as you.
I couldn't even imagine that anything so trivial could stand in the way of me making a life with someone I really cared about. Personally if I had a friend that told me this I would advise them to speak to a counsellor or someone similar about it (even before speaking to your partner about it).