In their fervent desire to rationalize Msgr. Marcel Lefebvre's resistance to Papa Wojtyla some traditionalists have for years promoted a libelous falsehood about St. Liberius, who governed the Church of Rome from 352 until his death in 366. According to the narrative, which I believe originated or was first promoted in the writings of Michael Davies, Liberius was put under political or physical duress, signed a heretical Arian statement about the nature of Christ, and excommunicated the Patriarch of Alexandria, Athanasius. Now we remember Athanasius as a courageous saint and Liberius as the first pope not to be a saint. History begs to differ.
As is always the case in the first millennium, the Byzantine emperor attempted to intervene in the Church's matters and impose his self-interested will rather than let ecclesiastical authorities resolve matters. At the time, in the middle of the fourth century, most of the bishops, but not the laity or lower clergy, had signed on to the Arian heresy despite the orthodox creed promulgated decades earlier in Nicaea. St. Athanasius of Alexandria most vehemently opposed the heresy and his enthusiasm was shared by no less than the pope at the time, Liberius. Local forces drove Athanasius from his office, but the pope proved a harder task. The sniveling egotist Constantius more or less kidnapped the pope—as would happen with the occasionally orthodox Vigilius—and dragged him before his court, where the emperor asked the pope, "Why do you support Athanasius against the world?" (the origin of the phrase Athanasius contra mundum). The pope recommended that the emperor convert to Christianity and was promptly sent into exile on Thrace while an imposter took his place in Rome. At this point some letters of dubious authenticity began to circulate in which the pope seemingly endorsed the Arian doctrine. Years later he returned to Rome where he died.
Several years ago the Transalpine Redemptorists posted a link to a now defunct blog that sought to bring the truth about Liberius to light. Far from being held as a heretic who signed a formula of heterodoxy, Liberius was seen as a saint and a hero, drawing ire only from the curmudgeonly St. Jerome. St. Ambrose was particularly fond of Liberius, as was Our Lady, who saw fit to use him to build a church in her honor. He appears in numerous martyrologies from ancient times through the middle ages, until he somehow fell out of favor with Bellarmine's Papalcentric view of the Church and was discarded from the Roman Martyrology. Still, his cult did not die so quickly. A statue of "S. Liberius I" is perched in in a transept of the modern St. Peter's Basilica, dedicated in the 17th century. When St. Paul's Outside the Walls imploded in a fire in the 19th century the rebuilders included "S. Liberius" in the gallery of popes. Pius IX, in article 16 of his Quartus Supra to the Armenians, reminds the Church of Liberius' resistance. Byzantine Christians never un-canonized Liberius and continue to observe the saintly pope's feast on August 27th.
Be careful what you say about other people. It just might stick.