Well, aside from God alone, there is a societal push towards belief in a deity in almost all cultures, which would also provoke responses in S types. For each type, there is some sort of reason to be involved in some sort of spiritual or religious pursuit, although that's not true for individuals. In other words, there's some aspect of it that is appealing to different types in different ways.
And discussion is never doomed to failure

Proof might be -- it'd be hard to prove God, just like it's hard to prove the spirit. But that doesn't mean it'd be impossible to discuss it. Indeed, like I said, if someone doesn't allow the perception of another -- in other words, if someone who doesn't believe approaches a discussion with the idea that it is then not possible for anyone -- then discussion becomes much more difficult.
But this is why I don't really like talking religion; most religions believe that there is a single God in a single way and that it is different than the God of another. And yet, one can argue that all those Gods of different religions may actually be one and the same, only symbolized or perceived in different forms. Even though God might be "different" to each religion, He is still universally there -- just in different forms. So in other words, even though everyone perceives something different, there is a much bigger picture that brings all that together to a single entity.
Or, that is what I believe. This is not a generally accepted thing or anything -- it's what I've come to theorize through personal meditation, research, and thought on the subject.