It's tragically ironic that in a Church which claims to be so devoted to loving marriage relationships, when one spouse changes their mind about the validity of the Church, this can threaten a previously healthy and happy marriage. It was a challenge in my marriage, when I learned the Church wasn't what it claimed to be, just like it is a real challenge for other people I've talked to about this issue.
How could a change of opinion threaten the stability of a previously healthy and fulfilling relationship? If you look at it logically, at least from a Mormon perspective, it makes perfect sense. For example, if the purpose of life is to make it back to heaven as eternal couples, and if temple marriage and faithfulness in the Church is necessary for salvation, then if one spouse leaves the Church, the need for the other to separate from the heretic is obvious. The spouse, who has detached themselves from the blessings of the Church, cannot go to heaven, and neither can you if you stay with them since eternal marriage is required to salvation in the highest level of the celestial kingdom. In a conversation my spouse had with her Dad, he admitted that the option of her divorcing me over my loss of faith "had crossed his mind."
Despite the fact that the premise of this argument is false (there is not a shred of evidence that "eternal life" exists, or that marriage in a Mormon temple is required to get there) this belief is ingrained and widespread in the Church. It's Mormon doctrine that we accept on faith. And if a Mormon has been indoctrinated since they were children about the need for temple marriage and enduring in faithfulness to the end, then having a spouse leave the Church can be one of the most challenging events in their marriage - on par with becoming unemployed or losing a child. Although I don't have any data to validate my suspicion, I suspect it's a common cause for divorce in the Church.
This, of course, is a tragic event: to throw away a loving and fulfilling marriage because your spouse changed their opinion. Think about it: all that happened is that someone changed their mind! No sin has been committed, no affair has occurred. The husband may still be a wonderful father and provider, the wife may be a devoted spouse and mother. But if someone doesn't think the Church is what it claims to be - the Kingdom of God on earth - then divorce may ensue because you can't make it to heaven being married to a heretic.
Part of the shock to my wife, when I changed my mind about the truth claims of the Church, was that I had somehow become a different person. This is also a very common reaction among extended family. If I could go from being a member of the bishopric one day, to being an apostate the next, then what other surprises could I spring on her? If I could suddenly leave the Church (it may have appeared sudden to her, but was much more gradual to me) then could I suddenly leave her and my kids too? As crazy as this sounded to me, this is how she (who is extremely intelligent and rational) sincerely felt at one point. Such is the power of religious faith and fear.
Of course I wouldn't! I still loved her and my children just as much as I did before (and I would need their support and understanding more than ever). I was the same person I was before. I had only changed my mind about the Church based on the facts I had honestly discovered through sincere and open minded research. But in the absolutist, black and white world of Mormon dogma, there are some things you just can't change your mind about. And the validity of the Church is one of them. It threatens everything.
However, our story has a happy ending. Two years after I told my wonderful companion that I didn't believe in the Church anymore, we are still happily married, and we respect each other's religious opinions - of which we mostly agree, but not completely. We largely agree on the big points, and appreciate the subtler differences of opinions we have. That is what makes conversations and relationships interesting after all.
We have always been good at communicating our differences, and this event tested our skills of communication to the breaking point. We stayed up many nights, talking, pleading, debating, and crying with each other over the truthfulness of the Church and how to raise our family when parents don't agree about religion. We went to bed many nights frustrated and dejected. Sometimes I didn't know for sure if our marriage was going to make it. We had some tough times - the divorce word even came up once. I think this scared her so much, that the spell the Church had on her was broken. She saw that she might just throw away everything we had built together, over something as unimportant as whether Joseph Smith was a prophet or a charlatan. My extreme sorrow at the prospect of separating from the love of my life, and my best friend in it, reassured her that the most important thing in the world to me - was her. I remember feeling that the Church was more important to her than I was, and she remembers feeling that "the truth" was more important than she was. This is how the Church conditions you to think: as long as we both put God and the Church first in our marriage, then our eternal relationship was safe. But if you question the Church, or God, then suddenly your marriage may be undermined. How messed up is that?
In retrospect, my big problem was that I thought I could convince her with logical arguments and historical facts. I remember thinking: "If I could just get you to know what I know, you would understand." The problem is that you can't do this. People must discover it themselves, at their own pace. I was trying to convince her with what was most convincing to me. Really what I needed to do mostly, was reassure her more that I loved her unconditionally and that I would never leave despite our differences of opinions. Although my faith in religion was dashed to pieces, my faith in my spouse was as strong as ever, and I needed her faith in me to stay strong too. I needed to be patient, and allow her to process my decision at her own pace. I needed to let her discover the truth about the Church on her own timeline, not force her to discover it on mine. It wasn't until I was deployed to Iraq, and she had some time to explore the books about the Church on her own, that she could think and discover what I knew already.
And she did.