When we talk of those who have "lost faith", I never assume they have acted intentionally through malice, or succumbed to sin, or rejected the concept of prophets, or any other possibility. If they state one of those paths openly and are vitriolic in their approach, I will accept that as real. Otherwise, I will sit down, take the time to discuss and understand their journey and provide whatever advice or counsel or listening ear or sympathetic heart I can. I will try to understand them without pre-conceived assumptions and, if possible, help them find a way to hold onto a sliver of hope even if they can't find faith. If that is not possible, and they feel they must leave the Church, I will accept their decision as their own, maintain whatever level of interaction is possible and make sure they know I am still their friend regardless of their faith at the time.
If they want to talk religion, I will talk religion; if they want to play board games, I will play board games; if they want to talk politics but not religion, that is what we will do. If we have not had a relationship in which we could talk religion, I will not talk religion - unless our relationship changes enough to do so later. In that situation, I will look and pray for an opportunity to share my testimony and any spiritual insight I can share, but I will share only if I feel strongly and uniquely prompted to do so. In summary, I will do my best to respect their agency and their stated desires - unless they are acting in such a way that I feel others are in danger. Then, and only then, will I upbraid or chastise or preach without invitation or call to repentance.
In my individual callings, I might have occasion to modify that slightly, but that's how I try to handle the balance as an individual. If I'm going to make a mistake, I want that mistake to be on the side of compassion and charity and brotherhood, not the alternative.This philosophy allows me to have many good and valuable friendships with people who can't be friends with other members - solely because those other members refuse to respect and accept my friends for who they are. They share my desire to see these friends embrace the Gospel but are unwilling / unable to wait for it to happen according to these friends' agency and the Lord's timetable. All too often , this unwillingness to "wait upon the Lord" drives my friends away and makes it very hard for others to reach them without defensiveness on their part.