Perhaps this timeline of Catholic statements re: religious liberty will be useful:
180 A.D. - Melito of Sardis criticized the Roman persecution which had been enacted against Christians, saying it is “not fit to be executed even against barbarian enemies.” By these words he showed that he did not think either Christians or pagans should be persecuted. This is a very pro-toleration principle. (Apology to the Emperor, in Eusebius, Ecclesiastical History, Book IV, Chapter 26, Paragraph 6)
213 A.D. - Tertullian said: “It is a fundamental human right, a privilege of nature, that every man should worship according to his own convictions: one man’s religion neither harms nor helps another man. It is assuredly no part of religion to compel religion—to which free-will and not force should lead us.” (Ad Scapulam, chapter 2)
308 A.D. - Lactantius said: “Religion, being a matter of the will, cannot be forced on anyone. In this matter it is better to employ words than blows. Of what use is cruelty? What has the rack to do with piety? Surely there is no connection between truth and violence, between justice and cruelty.” (De Divinis Institutionibus 5, 10)
598 A.D. - Pope Gregory the Great said: “[The Jews] should in no way suffer through a violation of their rights [by the Church].” “Rather let them enjoy their lawful liberty to observe and to celebrate their festivities, as they have enjoyed this up until now.” (Admonition of Paschasius) “During his pontificate, he put these words into practice, intervening to protect Jews from violence.” (
catholicculture.org/culture/library/view.cfm?recnum=4705)
624 A.D. - St. Isidore of Seville criticizes King Sisebut regarding his religious policy: “At the beginning of his reign he forced the Jews into the Christian faith, indeed acting with zeal, ‘but not according to knowledge’ [Romans 10:2], for he compelled by force those who should have been called to the faith through reason.” (History of the Goths, Vandals, and Suevi, 60–61, as translated in Kenneth-Baxter-Wolf, Conquerors and Chronicles of Early Medieval Spain (Liverpool 1990) 106–107.)
787 A.D. - St. Alcuin of York said: “Faith is a free act of the will, not a forced act. We must appeal to the conscience, not compel it by violence. You can force people to be baptised, but you cannot force them to believe.” He was confronting Charlemagne over his recent decision to force Saxon pagans to be baptized or be killed, and as a result of this confrontation Charlemagne abolished the death penalty for paganism. (Needham. Two Thousand Years of Christ’s Power, Part Two: The Middle Ages. Grace Publications, 2000. p. 52.)
866 A.D. - Pope Nicholas I said: “Concerning those who refuse to receive the good of Christianity and sacrifice and bend their knees to idols, we can write nothing else to you than that you move them towards the right faith by warnings, exhortations, and reason rather than by force, proving that what they know in vain, is wrong. … Furthermore, violence is never in any way to be inflicted upon them to make them believe. For whatever is not from an inner desire [ex voto], cannot be good.” (Ad consulta vestra, Response of Nicholas I to the Bulgarians)
1065 A.D. - Pope Alexander II said: “Although We have no doubt it stems from the zeal of devotion that your Nobility arranges to lead Jews to the worship of Christendom…you seem to do it with a zeal that is inordinate. For we do not read that our Lord Jesus Christ violently forced anyone into his service, but that by humble exhortation, leaving to each person his own freedom of choice, he recalled from error whomsoever he had predestined to eternal life, doing so not by judging them, but by shedding his own blood. Likewise, the blessed Gregory forbids, in one of his letters, that the said people should be drawn to the faith by violence.” (Letter Licet ex to Prince Landolfo of Benevento)
1201 A.D. - Pope Innocent III said: “It is contrary to the Christian religion to force others to into accepting and practicing Christianity if they are always unwilling and totally opposed.” “The one who never consents and is absolutely unwilling receives neither the reality [rem] nor the character [characterem] of the sacrament because express dissent is something more than not consenting at all.” (Letter Maiores Ecclesiae causas to Archbishop Humbert of Arles)
1274 A.D. - St. Thomas Aquinas said that Christians “[do] not indeed [wage war] for the purpose of forcing [non-Christians] to believe.” “Even if [Christian forces] were to conquer [the pagans], and take them prisoners, they should still leave them free to believe, if they will.” (Summa Theologica, II-II, Question 10, Article 8.)
1482 A.D. - In 1482 A.D. Pope Sixtus IV sent a letter to the Spanish king rebuking him for the abuses he was committing in the Inquisition: “Provoked by the complaints of many men against this, we desire to and are bound to provide that the office [of the Inquisition] itself is duly carried out by such means that no one is unnecessarily and unjustly harmed. … In the example of [Jesus], whose vicar we are on earth (cujus vices gerimus in terris), not willing the death of sinners but rather desiring to restore their salvation, we choose to show mercy rather than to punish.” He instituted several humanitarian reforms so that the victims of abuses could find safety from abusive Inquisitors. (Papal Bull Ad Perpetuam Rei Memoriam, reproduced in page 587 of Volume 1 of Henry Charles Lea’s “A History of the Inquisition of Spain.”)
1528 A.D. - St. Thomas More wrote that violence should not be used against heretics even by secular authorities, unless the heretics themselves are violent, and then only for that reason. (Dialogue Concerning Heresies, Part IV, Chapter 13)
1634 A.D. - The state of Maryland is founded by Catholics with the express purpose of being a safe-haven where religious liberty will be respected.
And so forth.