First, a quote from the Second Vatican Council:
The Church regards with esteem also the Moslems. They adore the one God… [Second Vatican Council; Nostra Aetate; 3; source]Next, from the Catechism itself (cited in my previous post):
The plan of salvation also includes those who acknowledge the Creator, in the first place amongst whom are the Muslims; these profess to hold the faith of Abraham, and together with us they adore the one, merciful God, mankind's judge on the last day. [Roman Catholic Catechism; 841]And finally, from a pope:
Then we see another circle around us. This too is vast in extent, yet not so far away from us. It comprises first of all those men who worship the one supreme God, whom we also worship...we have those worshipers who adhere to other monotheistic systems of religion, especially the Moslem religion. We do well to admire these people for all that is good and true in their worship of God. [Pope Paul VI, Ecclesiam Suam; 107; source]The Roman Church, however, did not always have such kind words to say regarding the religion of Islam. A Roman Catholic ecumenical council, held during the middle ages, wrote these words regarding the Holy Land:
Alas! the very land in which the Lord deigned to work our salvation and which, in order to redeem humanity by payment of his death, he has consecrated by his own blood, has been boldly attacked and occupied over a long period by the impious enemies of the Christian name, the blasphemous and faithless Saracens. [Second Council of Lyons; First Constitution; source]Whereas the Roman Catholic church, its leaders, and its faithful today claim that Muslims worship the same true God, the Roman Catholic church of the middle ages called Muslims "impious enemies of the Christian name," saying they were "blasphemous and faithless Saracens" (the medieval name for Arabic Muslims). They would not have agreed with the Roman Catholic Catechism that "together with us [Muslims] adore the one, merciful God."
The Roman Church likewise taught a number of things throughout history regarding interaction with Muslims...much of it not very friendly. For example, Christians were commanded not to work for them, or live with them - in fact, you could be excommunicated for doing so:
Jews and Saracens are not to be allowed to have Christian servants in their houses, either under pretence of nourishing their children or for service or any other reason. Let those be excommunicated who presume to live with them. [Third Lateran Council; Canon 26; source]Likewise, Christian leaders were commanded to forbid the worship of Muslims:
It is an insult to the holy name and a disgrace to the Christian faith that in certain parts of the world subject to Christian princes where Saracens live, sometimes apart, sometimes intermingled with Christians, the Saracen priests commonly called Zabazala, in their temples or mosques, in which the Saracens meet to adore the infidel Mahomet, loudly invoke and extol his name each day at certain hours from a high place, in the hearing of both Christians and Saracens and there make public declarations in his honour. There is a place, moreover, where once was buried a certain Saracen whom other Saracens venerate as a saint. A great number of Saracens flock there quite openly from far and near. This brings disrepute on our faith and gives great scandal to the faithful. These practices cannot be tolerated any further without displeasing the divine majesty. We therefore, with the sacred council's approval, strictly forbid such practices henceforth in Christian lands. We enjoin on catholic princes, one and all, who hold sovereignty over the said Saracens and in whose territory these practices occur, and we lay on them a pressing obligation under the divine judgment that, as true Catholics and zealous for the Christian faith, they give consideration to the disgrace heaped on both them and other Christians. They are to remove this offence altogether from their territories and take care that their subjects remove it, so that they may thereby attain the reward of eternal happiness. They are to forbid expressly the public invocation of the sacrilegious name of Mahomet. They shall also forbid anyone in their dominions to attempt in future the said pilgrimage or in any way give countenance to it. Those who presume to act otherwise are to be so chastised by the princes for their irreverence, that others may be deterred from such boldness. [Council of Vienne; Decree 25; source]In addition to clear commands to "Catholic princes" to forbid the worship of Islam (indeed, to expel it from their lands in an "obligation under the divine judgment"), we likewise see strong language against Islam. Muhammad is called an "infidel," and the worship presented by Muslims is called an "offence," with toleration of their worship and pilgrimages being displeasing to "divine majesty." Christian leaders permitting Muslims to worship freely and without hindrance is said to not only be an "insult to the holy name," but "a disgrace to the Christian faith." No doubt the clergy who penned the words at Vienne would be shocked to hear the words of Pope Paul VI that Muslims and Catholics together "worship the one supreme God," as well as his words that Catholics "do well to admire these people for all that is good and true in their worship of God."
No doubt some will desire to pull a tu quoque and argue that non-Roman Catholics (even some of the first Protestants) have likewise said hostile words regarding Muslims and other non-Christians. The point, however, is that Roman Catholics deny the statement from Martin Luther that popes and councils contradict one another...yet here, they plainly do. Keep in mind these are not general councils, but rather they are considered ecumenical to Rome (and hence binding), and we have quoted a legitimate pope (not an "anti-pope"). Yet reviewing the teachings in one and then the other, it almost seems as if these are two separate churches.
Some will also probably argue that these are merely referring to specific events in history, and hence should be seen in that context. While it is true some of these canons and decrees were written during the Crusades (or were during a time when another crusade was trying to be started up), they clearly use general language in regards to Muslims, their worship, and Christian interaction with them. Some (such as the quote from the Third Lateran Council) likewise includes the Jews alongside the Muslims. Again, there is a clear contradiction not only in how Christians are told to interact with Muslims, but (more importantly) how the religion of Islam is seen by the Roman Church. On the one hand, Muslims are called faithless and blasphemous; on the other hand, Muslims are said to worship the same God as Christians do. On the one hand, Catholics are commanded not to work for Muslims, live with Muslims, or let Muslims worship; on the other hand, Catholics are told "to work sincerely [with Muslims] for mutual understanding...social justice and moral welfare, as well as peace and freedom" (Nostra Aetate).
While I don't deny Christians should treat Muslims with grace, we have to use this to examine the claim by Roman Catholics that their church has been preserved by the Holy Spirit from error, and has always been consistent in their teaching. What we see here, however, is a clear development and change in Rome's understanding of how to respond to Muslims and the false religion that is Islam, as well as whether or not to even consider them a completely false religion. I've spoken to Roman Catholic laymen online who become appalled if you even suggest Muslims worship a false God, and do so by providing the quotes given at the start of this post. One can only imagine what they would think if the quotes from the Church of Rome in centuries past would be presented to them. They would either have to rationalize how the two groups work together (which would require some serious mental compartmentalization), or they would have to borrow the Muslim teaching of abrogation to forsake the more embarrassing decrees and canons (which would contradict the notion that popes and ecumenical councils can teach error).
The unfortunate truth is that the Roman Catholic church is like any other church: it is subject to change and modify its beliefs and expressions according to the winds of time, unless some kind of anchor is put in place. Roman Catholics attempt to put their faith in the magisterium, but the magisterium is made up of men, like you and I, and men can prove fickle. This is how you can get a Roman bishop hundreds of years ago calling Muslims "impious enemies of the Christian name," while a Roman bishop hundreds of years later says of Muslims "together with us they adore the one, merciful God." It is not an anchor which can prevent one from teaching error, just as any Roman Catholic is erring who thinks Muslims, in any way, shape, or fashion, are worshiping the true God.
The question therefore is, if your church, which you claim has not changed or cannot change, does indeed change and transform its beliefs, is it being led by the Holy Spirit, or is it being led by men and the rationality of men? No church is perfect, of course - only Christ is perfect. However, if you find yourself attempting to compartmentalize, you must realize that you are being dishonest. If your church forces you into dishonesty, is it truly led by God? These are things for Christian faithful to meditate on.