"Not to oppose error is to approve it, and not to defend the truth is to suppress it, and indeed to neglect to confound evil men, when we can do it, is no less a sin than to encourage them." Pope St. Felix III
“Alas, Most Holy Father! At times, obedience to you leads to eternal damnation.” St. Catherine of Siena, Letter to Pope Gregory XI
“What then should a Catholic do if some portion of the Church detaches itself from communion of the universal Faith? What choice can he make if some new contagion attempts to poison, no longer a small part of the Church, but the whole Church at once? Then his great concern will be to attach himself to antiquity which can no longer be led astray by any lying novelty.” St. Vincent of Lerins, Commonitory, Chapter 3, Section 7
"A manifest heretic is Not a Christian, as is clearly taught by St. Cyprian, St. Athanasius, St. Augustine, St. Jerome and others." St. Robert Bellarmine (1542-1621 AD), Church Doctor, "Prince of Apologists"