Let’s simplify the discussion a bit. The intellect and emotion are two different aspects of the personality. They interact much, but each manages its affairs differently. There are intellectual disbelievers, and these comprise the realm of apikorsim. These are few and far between. The Kotzker rebbe describes this at great length (atypical for his style of sharp, brief witticisms). He states that what we tend to call apikores is actually nothing better than a baal taavah, looking for a verbal excuse for following hedonistic pleasures.
Most people do not engage in deep philosophical investigation and reach a logical conclusion that there is no god, or that someone else it it. Rather, those who choose these ideologies are doing so because it provides then a (PC) explanation for doing what they want. This process is emotion driven, not logic. The reason we should not waste time talking theology with someone who is OTD is because that is not the type of issue.
OTD kids are not even doing what they do because they are attracted to those behaviors. I have yet to meet a single OTD kid that went that direction because of the internet or the movies, or the opposite gender, of because they liked dressing differently. They are always escaping something related to their experience within their frum community, usually some combination of what they experienced at home and school. This escape is emotional in nature. The cure is not a solid philosophical lecture that proves to them that their way is logically bankrupt. That has been tried, and fails 100% of the time. A little love and acceptance, and the experience of the beauty of Torah and mitzvos works. The emotional angle is all that is effective.
I hope this simplifies the discussion.