A story about Republican presidential candidate Michelle Bachman’s former church, includes a nice, brief summary of early Protestant rift with the Roman Catholic Church and why Martin Luther came to refer to the Pope as anti-Christ.
[Terrence] Reynolds, of Georgetown University, says that this view of the papacy, alarming though it may be to the modern political world, has, over the centuries, shaped the rise of Protestantism. “The discussion of the papacy arose during the vitriolic exchanges Luther had with the Roman Catholic Church during the Reformation,” he explained. “Luther thought [the Scripture] proclaimed clearly that we are saved by grace and that faith alone is what justifies us before God; for Luther those claims were the fundamental teaching of the Scripture and should be the focus of the Church’s proclamation.”
But the Roman Catholic Church insisted that faith alone was insufficient, and that good works dictated and overseen by the church were necessary for salvation. “As the debates continued,” Reynolds said, “Luther became more and more frustrated with Rome’s rejection of justification by grace alone through faith and began to link the Church’s intransigence on this matter with Scriptural references to the Antichrist. According to the Scripture, anyone who seeks to undermine the purity of the Gospel and the clear teaching of Scripture in the name of the Gospel–or anyone who becomes anti-Gospel–is the Antichrist. So Luther made the claim** that the Pope is the Antichrist, insofar as the Pope insists upon obedience to his office and on work righteousness, both of which demean the atoning work of Christ.”
John Meunier 
I actually wonder if Luther got as incensed about “works” as we Protestants like to make out. I think the more central piece of the struggle was where the authority lie for the interpretation of Scriptures. Could learned men (they were all men at that time) like Luther hear God in Scripture because Scripture interpreted itself? Or is Scripture so obscure that it could only be finally interpreted through the ageis of the Church and the Pope?
Ignatius of Loyola – who was a contemporary of Luther – got charged in ecclesial court of being a “crypto Lutheran”. This charge makes sense if we see the dispute being over the interpretation of Scripture. It makes no sense under the “faith versus works” argument.
I found it interesting that the article implied the WELS view is a small minority opinion within Lutheranism when, as noted by the writer, the Smalcald Articles state, “”This teaching shows forcefully that the Pope is the very Antichrist, who has exalted himself above, and opposed himself against Christ, because he will not permit Christians to be saved without his power, which, nevertheless, is nothing, and is neither ordained nor commanded by God ” (Smalcald Articles, Part II, Article IV; Of the Papacy).
It is important to note that the LCMS requires of its pastors to hold a quia subscription to the Book of Concord, part of which is composed by the Smalcald Articles. As such, the view of the pope as Antichrist must by default be affirmed by the LCMS. This gives the story a different hue, in my opinion. Far from a response to a political candidate who belongs to a small denomination, the article actually touches on the official denominational teachings of nearly half the Lutherans in the United States.