Luther: Are Those Who Defend the Roman Church Christians?

An interesting study is Luther's change in attitude to the Roman Church and those who remain in her. I've covered this topic before: Myth #11: Luther thought that the Roman Church was no longer a true Christian Church.

As a supplement, here's a quote from Luther from 1541. These are strong words from Luther directed at those who defend the Papacy:

Here they might say and probably will say, “Why do you depict us shamefully as a new, apostate church, when we have baptism, the sacrament, the keys, the creed, and the gospels, just like the ancient church from which we derive? Haven’t you already admitted above that we, as well as you, derive from the ancient church?” I answer, “It is true, I admit, that the church in which you sit derives from the ancient church as well as we, and that you have the same baptism, the sacraments, the keys, and the text of the Bible and gospels. I will praise you even further and admit that we have received everything from the church before you (not from you). What more do you want? Are we not devout enough? Will you not call us henceforth unheretical? We do not regard you as Turks and Jews (as was said above) who are outside the church. But we say you do not remain in it but become the erring, apostate, whorelike church (as the prophets used to call it), which does not remain in the church, where it was born and brought up. You run away from this church and from your true husband and bridegroom (as Hosea says of the people of Israel [Hos. 1:2]) to the devil Baal, to Molech and Astaroth. Do you understand that?” I will explain.
You were indeed all baptized in the true baptism of the ancient church, just as we were, especially as children. Now if a baptized child lives and then dies in his seventh or eighth year, before he understands the whorelike church of the pope, he has in truth been saved and will be saved—of that we have no doubt. But when he grows up, and hears, believes, and obeys your preaching with its lies and devilish innovations, then he becomes a whore of the devil like you and falls away from his baptism and bridegroom—as happened to me and others—building and relying on his own works, which is what you whoremongers preach in your brothels and devil’s churches; whereas, by contrast, the child is baptized to rely and build on his one dear bridegroom and Lord, Jesus Christ, who gave himself for us. It is as if a devout man were to bring up a poor, young, servant beggar girl as his future bride and become betrothed to her, and she were to keep herself pure until she came to womanhood, and then turn her attentions elsewhere and look at other men who pleased her better, and let herself be persuaded by them and become passionately desirous of them, thus abandoning her true, devoted bridegroom, who had rescued, nourished, educated, clothed, adorned, and treated her well, and let herself be made a whore by everyone. This whore, who before was a pure virgin and dear bride, is now an apostate, erring, married whore, a house-whore, a bed-whore, a key-whore, being the mistress of the house, having the key, the bed, the kitchen, the cellar, and everything at her command. Yet she is so evil that beside her the common unattached whores, the pimp-whores, the whores of the field, the country, and the army are almost holy. For she is the true arch-whore and the true whore of the devil.
Of such a whore Hosea speaks, and Ezekiel indeed does so much more coarsely, in fact almost too coarsely, in chapter 23. You should read that if you want to know what kind of a whore your church is. For this is what I mean when I call you an apostate, erring whore—you who were baptized as children in the dear Lord and even lived some years like the ancient church. But when you grew up and reached the age of reason (as I and everyone else have done), you saw and heard the lovely ceremonies of the papal church, and also its glittering profit, honor, and power, yes, its magnificent holiness, the mighty worship, and all the yarns about the kingdom of heaven. Then you forgot your Christian faith, baptism, and sacrament, becoming the diligent pupils and young little whores (as the comedies say) the procuresses, the arch-whores, until you old whores once more make young whores. Thus the church of the pope, indeed, the church of the devil, grew, transforming many of Christ’s young virgins, who were born in baptism, into arch-whores. This, I hold, should be said in German, so that you and everyone can understand what we mean. For if you hold these innovations of yours to be a joke—you who neither have a God nor honor him—then it is something terrible and abominable before God. It is idolatry, murder, hell, and every calamity, which God cannot bear, so that he will damn the arch-whore for eternity.
St. Peter prophesies about that when he speaks of you, that is, of such new prophets and churches in II Peter 2 [:18–19], “For, uttering loud boasts of folly, they entice with licentious passions of the flesh men who have barely escaped, and who must now walk in error. They promise them freedom, forgiveness, and indulgences, but they themselves are slaves of corruption.” And again, “For if, after they have escaped the defilements of the world through the knowledge of our Lord and Savior Jesus Christ, they are again entangled in them and overpowered, the last state has become worse for them than the first. For it would have been better for them never to have known the way of righteousness than after knowing it to turn back from the holy commandment delivered to them. It has happened to them according to the true proverb, the dog turns back to his own vomit, and the sow is washed only to wallow in the mire” [II Pet. 2:19–22]. That is what you are, and that is what I was. There you have your new apostate erring church sufficiently described in German and portrayed clearly enough for you to see. We acknowledge not only that you have, with us, come from the true church and been washed and made clean in baptism through the blood of our Lord and Savior Jesus Christ, as St. Peter says here, but also that you are in the church and remain in it. Indeed, we say that you sit and rule in it as St. Paul prophesied in II Thessalonians 2 [:3–4], that the accursed Antichrist would sit (not in the cowshed), but in the temple of God. But you are no longer of the church, or members of the church, for in this holy church of God you are building your own new apostate church, the devil’s brothel with limitless whoredom, idolatry, and innovation, by which you corrupt those who have been baptized and redeemed along with yourselves. And you swallow them down through the jaws of hell into the abyss of hell itself, with a countless multitude, along with the terrible wailing and deep sorrow of those who see this with spiritual eyes and recognize it.

Luther, M. (1999, c1966). Vol. 41: Luther's works, vol. 41 : Church and Ministry III (J. J. Pelikan, H. C. Oswald and H. T. Lehmann, Ed.). Luther's Works (41:207). Philadelphia: Fortress Press.