"Even if the Pope were Satan incarnate, we ought not to raise up our heads against him, but calmly lie down to rest on his bosom": A reasonably faithful pastiche

"Even if the Pope were Satan incarnate, we ought not to raise up our heads against him, but calmly lie down to rest on his bosom. He who rebels against our Father is condemned to death, for that which we do to him we do to Christ: we honor Christ if we honor the Pope; we dishonor Christ if we dishonor the Pope. I know very well that many defend themselves by boasting: 'They are so corrupt, and work all manner of evil!' But God has commanded that, even if the priests, the pastors, and Christ-on-earth were incarnate devils, we be obedient and subject to them, not for their sakes, but for the sake of God, and out of obedience to Him."

     St. Catherine of Siena, as quoted by Michael Warren Davis in "Pray for the Pope," First things, 10 December 2018, and often (and earlier) elsewhere, but without a reference.
     My current sense is that this is authentic, but a pastiche.  At the moment it looks to me like this comes from two separate passages in Letter 17 (Dupré Theseider =28 Tommasèo =191 Gigli) to Bernabò Visconti of Milan plus two somewhat more closely contiguous passages in Letter 68 (Dupré Theseider =207 Tommasèo =198 Gigli) to the Signori of Florence.  To see this you need the original Italian, which I've taken from the edition edited by Tommasèo and inserted into the standard Noffke translation:

"Even if the Pope were Satan incarnate, we ought not to raise up our heads against him".  Noffke, vol. 1, p. 69:  "Even if that vicar [of Christ] were a devil incarnate, I must not defy him but always humble myself [(io non debbo alzare il capo contro a lui, ma sempre umiliarmi)] and ask for the blood [of Christ] for mercy’s sake."  Note that "io non debbo alzare il capo contro a lui" (from Tommasèo, vol. 1, p. 119) would be, more literally, "I must not raise my head [(alzare il capo)] against him."

"calmly lie down to rest on his bosom".  Noffke, vol. 1, p. 71:  "I would have us humbly rest our heads on the lap of Christ in heaven [(Umilmente voglio che poniamo il capo in grembo di Cristo in cielo)] by our affection and love, and [on the lap] of Christ on earth (his deputy) by our reverence for the blood of Christ, to which he holds the keys."  Note that "grembo" (from Tommasèo, vol. 1, p. 121) can be translated, out of modern Italian at least, as "lap, womb, bosom".

"He who rebels against our Father is condemned to death, for that which we do to him we do to Christ: we honor Christ if we honor the Pope; we dishonor Christ if we dishonor the Pope."  Noffke, vol. 1, p. 214:  "whoever like a gangrenous limb rebels against holy Church and against our father, Christ on earth [(alla santa Chiesa, e al padre nostro Cristo in terra)], has fallen under the sentence of death [(è caduto nel bando della morte)], because whatever we do to him we are doing to Christ in heaven, whether it is reverence or dishonor."  Italian from Tommasèo, vol. 3, p. 251.  This match is less clear than the other three considered as a quotation (rather than a paraphrase), and especially when one considers how often St. Catherine repeats herself.

"many defend themselves by boasting: 'They are so corrupt, and work all manner of evil!'  But God has commanded that, even if the priests, the pastors, and Christ-on-earth were incarnate devils, we be obedient and subject to them, not for their sakes, but for the sake of God, and out of obedience to Him."  Noffke, vol. 1, 215:  "they defend themselves by saying [(dicendo)], 'They are bad, and they are doing all kinds of evil.'  But I am telling you that God wills, and has so commanded [(Dio vuole, e ha comandato così)], that even if the pastors and Christ on earth [(pastori, e Cristo in terra)] were devils incarnate (rather than good kind fathers), we must be submissive and obedient to them—not for what they are in themselves but out of obedience to God, because they take the place of Christ, who wants us to obey them."  Italian from Tommasèo, vol. 3, p. 251-252.