1. Catholicism teaches papal infallibility, the doctrine that the Pope cannot err on matters of faith and morals.
2. Pope Leo X said, "All ages can testifie enough howe profitable that fable of Christe hath ben to us and our companie."
3. But Christ is not a fable, and so Pope Leo X was not infallible.
4. Therefore, Catholicism is false.
Pope Leo X (1475-1521) never said this. The quote comes from the satire The Pageant of the Popes by Protestant John Bale (1495-1563).