My guess is that there is more than this for them to ban you. Perhaps more misunderstandings, but this sounds more like one of those incidents that touch the limit and they "had it with you"! (shame on them).
I'd try to spend time understanding more where they are coming from to find a way to make things work. That doesn't mean that you and them need to become best friends, not at all, but it is important that all of you can have at least a peaceful relationship, even if it is just superficial, specially if you are marrying your fiancee.

By the way, your fiancee is a keeper, I think it speaks tons about him the fact that he didn't go on that vacation and stood by you.

gab