[NOTE: I understand the fine line I am about to walk in this post, but I believe it is important to strive to walk it - and to err on the side of charity rather than judgment. My request is that anyone who reads this post recognize the disclaimers ("some, many, multiple, sometimes, etc.") I am using and not jump to any conclusion not articulated clearly in the post itself.]
I have unshakable confidence that "pure Mormonism" doesn't condemn automatically those who leave the LDS Church - that, in many cases, God will credit to them the fact that they are acting "according to the dictates of their own consciences" in the decisions they make. Those decisions are not made in a vacuum, and, often, we (the average membership who are not aware of intimate details) simply have no idea what factors lead to someone leaving. Personally, I am aware of multiple situations where I cannot argue with a decision to leave - nearly all of which involve circumstances that can be characterized legitimately as people being driven away by other members. I wish badly people would not leave, but, in some situations, I actually agree that leaving is better in the moment than staying.
The ideology of an Atonement wrought by someone who actually understands rejection and unfair treatment is FAR more powerful and expansive than is the Church and the membership, and that is a comfort to me - even as I mourn for those who suffer needlessly and unjustly. In fact, I think the power of the Atonement is most visible in just these cases - where the LDS membership can't quite grasp that some people who leave will be blessed every bit as much as those who never leave. We expect so much of "our own" (often so unrealistically) and see through our own glasses so darkly when it comes to how WE let them down and drive them away - and, while I realize how natural that tendency is, I wish badly that we all could rise above it.
Until that time when we can, I am comforted by the assurance that they will be judged by One who sees, understands and loves them fully - in the same way that He sees, understands and loves me.