Within the context of a Catholic forum, and within a subsection of such a forum that is dedicated to philosophy, simply implying to a Catholic theist that they could be mistaken is indeed entirely foolish, irrelevant, and is disrespectful to their intellectual integrity and dexterity.
What, precisely, is the purpose of such a question? Are you silently warning the Catholic that they are headed towards dangerous waters, and are solemnly pleading with them to re-think their course? Are you perhaps expecting a detailed and intricate exposition of theistic apologetics? Or are you more nefarious in your intent, and simply wanting to stir pots and rattle cages? What?