When you bring in a third party to justify your position, it’s like putting lighter fluid on a burning barbecue. Your fiancé can’t help but feel angry, because bringing in your parents leads him to feel as if you’re ganging up on him with people not even present in the room. Whenever you unilaterally make your private relationship problems public, you introduce an additional issue to resolve. In this case, you have the original topic that you were trying to discuss and your decision to involve your parents. I suggest that you apologize for your communication mistakes and then do some more listening so that he feels truly understood.