Such discussions often become heated and unproductive for three basic reasons:
1. Are there really any “doubtful matters” concerning which we may disagree? Yes. One need only to spend time with the Eastern churches that are in full communion with Rome to see that there is lots of room for legitimate differences within orthodox belief and doctrine. And yet, in discussions one can routinely see de facto denial of that.
2. When the discussion turns from what is Catholic to who is Catholic: the turning point when anger and bitterness arise.
3. The implications of the involvement of the Holy Ghost (and Satan) in the Church are too enormous for us to handle well. (Spiritus Sanctus was routinely translated as “Holy Ghost” during Fr. Dudley’s time, but now it is usually translated as “Holy Spirit”–either is correct.) Implying–even without intending to do so–that you are on the side of God, and your discussion partner is on the side of Satan, often leads to strong emotional reactions.
4. Disagreements over our obligations–and their nature–as Catholics concerning loyalty and obedience towards authority. It is easy to say that God is truth, and all truth is God’s truth: but do we really believe that? For example, do we believe that we should tell the truth about our bishop or the Pope? We are told that the truth will set us free, so presumably we can largely know the truth, but what of humility? What of “detraction”? How to balance this all?