If the Potter books easily take away or divert from the teachings of the church, then the church is lax in nurturing it's sheep.
Sorry, bro, but I simply cannot understand your statement. Your 'IF' part does not connect with your 'THEN' part. If it is the Potter books that denies the teachings of the Church, then it is the Potter books that must be 'opposed'. If it is the believers that denies the teachings of the Church, then it is with the believers that the defense of the Faith must be made.
I am a Catholic but I refuse to go by "Roman Catholic" because to me that term means "universal" to call it a "Roman" kind of universal that would be a misnomer and oxy*****.
And I don't believe in the infallibility of the Pope or ex cathedra.
The Catholic Church never called itself the Roman Catholic Church in any of its official documents. Do you know where it started? Please find out. Furthermore, calling yourself Catholic does not mean you are one. Catholics are subject to the Pope and the bishops in communion with him. You surely are not Catholic as I am a Catholic. I believe and am convinced of the infallibility of the Pope in matters of faith and morals. I even doubt if you truly knew of
ex cathedra.