Papal infallibility is infallibly true because the pope taught it infallibly.
Without the backstop of the overall incorruptibility and Magisterial infallibility of the Church in general, the certainty of faith regarding the truth of papal infallibility is a circular reference.
But for those of us who believe in the overall infallibility of the Catholic Magisterium, we hold that the Pope infallibly defined infallibility on account of the INFALLIBILITY OF THE CHURCH ... which R&R basically deny, apart from infallibly defined truths, except that they unknowingly pull the rug out from under even that belief by undermining the foundation upon which it rests.
R&R, as articulated by many here, really is nothing but Old Catholicism except that, unlike the Old Catholics, they HAPPEN to judge that infallibility IS consistent with Tradition, with the "ancient Church," whereas the Old Catholics judge that it is not. So the difference here is purely accidental.