I've been in a few discussions recently on Luther's antisemitism [here and here]. The following is an excerpt from my paper, Martin Luther’s Attitude Toward The Jews. I compiled this section on John Eck before the advent of Google books, so perhaps more material and contexts are now available.
One of the leading Roman Catholic theologians of the sixteenth century was Johann Eck. He also wrote some virulent anti-Jewish tracts. Here we find two leading theologians of the Protestant Church (Luther) and the Roman Catholic Church both engaging in clearly anti-Christian attitudes. How could two of the best minds of the sixteenth century be so wrong and not realize it? Had it just been Luther, perhaps a critic could say: “See the basis of Protestantism is flawed and leads to anti-Semitism.” However, Johann Eck was considered a Roman Catholic theologian of great brilliance. He was respected and revered by the Papacy (and utilized by the Papacy!), and yet he also attacked the Jews unjustly:
“…Luther’s arch-antagonist John Eck published a similar treatise entitled Refutation of a Jew-Book (Ains Judenbuechlins Verlegung). Fulminating against the “cunning, false, perjured, thievish, vindictive, and traitorous Jews,” he decries the security and freedom they had hitherto been granted and recommends new and more stringent anti-Jewish laws.”
“The absolute nadir of anti-Jewish polemic in the early modern period was by Luther’s Catholic opponent Johannes Eck, whose 1541 Refutation of a Jew Book was ‘a summa of the anti-Jewish literature of the Middle Ages, leaving out no accusation of genocide, blasphemy, or treason.’ ”
“Could [the Jews] but drown all Christians in one spoon, said Johann Eck in the course of one of the most vicious of all anti-Jewish diatribes, ‘they would eagerly do it.”
“By the fifteenth and sixteenth centuries the campaign against Jewish physicians…attained a high pitch of virulence. No slander was too mean to be turned to account… ‘When they come together at their festivals, each boasts of the number of Christians he has killed with his medicine; and the one who has killed the most is honored,’ runs Johann Eck’s variation upon an inexhaustible theme.”
“In 1540, when another ritual murder charge was raised against the Jews in Sappenfeld, Eck wrote Refutation of a Jewish Booklet in which he explains that Jews needed Christian blood in order to wash away their own blood stains which God had inflicted on them because they had crucified Christ. He concludes that, ‘it is no wonder that the Jews now buy the blood of innocent children, just as their fathers had bought the innocent blood of Jesus Christ from Judas with thirty pennies.’ ”
“Although Johannes Eck, Luther’s dedicated opponent, and others wrote vitriolic attacks on the Jews, some of Luther’s collegues, such as his dear friend Justas Jonas, present at Luther’s deathbed, Andreas Osiander, reformer in Nuremberg, were very understanding of the position of the Jews.”
“When Osiander ventured to publish an anonymous tract defending Jews against the charge of ritual murder, Eck, knowing the true identity of the author, calls him the ‘evangelical scoundrel’ who dared to defend the ‘bloodthirsty Jews’. The Lutherans, Eck curses on, were all evil monks who had stirred up the Peasants War and were now defending the archenemies of Christendom… Eck concludes his long-winded vituperation by accusing Osiander of slander against the whole of Christianity, because by denying the truth of ritual murders, the evangelical reformer was in essence accusing Christians of murder, magic, and lies.”
“Luther’s Roman Catholic opponents frequently considered Luther to be a friend of the Jews. This was especially true in the early years of the Reformation, but even as late as the 1540’s, Eck considered the Lutheran Reformer Andreas Osiander to be a ‘Luther-son’ and thus a ‘Jew-father.’ In other words, Luther’s Catholic opponents attacked what they perceived to be his pro-Jewish opinions. This in turn led to the Counter-Reformation revival of medieval anti-Jewish perspectives out of concern that Jewish biblical interpretation supported Protestant teachings.”
A telling comparison can be made by consulting the way the Catholic Encyclopedia evaluates the anti-Jewish remarks of Johann Eck and Martin Luther. The Catholic Encyclopedia highly praises Eck: “He was the most distinguished theologian of the time in Germany, the most scholarly and courageous champion of the Catholic Faith. Frank and even in disposition, he was also inspired by a sincere love of truth; but he showed none the less an intense self-consciousness and the jovial bluntness of speech which characterized the men of that day.” Interestingly, the Catholic Encyclopedia makes no mention of Eck’s anti-Jewish writings.
However, in their entry on “Luther” they point out, “It was while in this agony of body and torture of mind, that his unsurpassable and irreproducible coarseness attained its culminating point of virtuosity in his anti-Semitic and antipapal pamphlets.” In the Catholic Encyclopedia’s entry on the “History of the Jews,” no mention is made of Johann Eck. However, of Luther they point out, “Luther himself, towards the end of his life, was [the Jews] greatest opponent,” and, “Luther, on the other hand, required their absolute expulsion. . . . It was reserved for him to place Jews on a level with Gypsies. . . . He was the cause of their being expelled by Protestant princes”
I submit that many Roman Catholics evaluate Luther’s anti-Semitism the same way the Catholic Encyclopedia does. The Catholic Encyclopedia fails to document that one of the leading theologians of the sixteenth century was blatantly hostile towards the Jews, but rather characterizes him to be “inspired by a sincere love of truth.” I’ve met many Roman Catholics in discussion who point out that Johann Eck defeated Luther in debate, and was a champion for the Roman Catholic Church. How many of them would dismiss the entirety of Eck’s work because he was blatantly anti-Semitic?
49] “Johann Eck, Vice-Chancellor of the University of Ingoldstadt, by common consent acknowledged as one of the foremost theological scholars of his day, endowed with rare dialectical skill and phenomenal memory…” [Catholic Encyclopedia: Luther entry].
 Most of Johann Eck’s writings were in Latin, but some feel that since his anti-Jewish writings were written in German, they were intended for a popular audience. In one of his anti-Jewish works, Eck perpetuates some of the leading anti-Jewish propaganda prevalent in his day, particularly the Jewish ritual murder of children and the taking of their blood. After documenting Eck’s work to substantiate a Jewish ritual murder, Mark U. Edwards notes, “Eck harbors no doubts about the authenticity of this ritual murder… This incredible story is only one of several alleged ritual murders related in the anonymous account and in Eck's treatise. It illustrates well, however, the improbability of the charge of ritual murder, while at the same time it shows that even highly educated men such as Johann Eck firmly believed such libels. Eck's whole treatise, Refutation of a Jew-book in Which a Christian, to the Dishonor of All Christendom Claims That Injustice is Done the Jews in the Accusation That They Murder Christian Children, published a year before Luther's most infamous treatises, is dedicated to proving, in reply to a Lutheran skeptic, that Jews did murder Christian children for their rituals; that they did desecrate the eucharistic host; and that they did do such things as poison wells and bewitch animals and ruin crops. These were the convictions of a scholar, writing in this case for a popular audience” [Mark U Edwards, Luther’s Last Battles, 120].
 LW 47:129.
Carter Lindberg, “Tainted Greatness: Luther’s Attitudes Toward Judaism and Their Historical Reception,” in Nancy A Harrowitz (ed.), Tainted Greatness: Antisemitism and Cultural Heroes (Philadelphia: Temple University Press, 1994), 17.
 Joshua Trachtenburg, The Devil and the Jews: The Medieval Conception of the Jew and Its Relation to Modern Anti-Semitism (Philadelphia: ThE Jewish Publication society of America, 1943), 182.
 Joshua Trachtenburg, The Devil and the Jews: The Medieval Conception of the Jew and Its Relation to Modern Anti-Semitism (Philadelphia: The Jewish Publication society of America, 1943), 93.
 R. Po-chia Hsia, “Jews as Magicians in Reformation Germany,” in Sander L. Gilman and Steven T. Katz, Anti-Semitism in Times of Crisis (New York: New York University Press, 1991), 119-120.
 Lewis W. Spitz, The Protestant Reformation (New York: Harper and Row Publishers, 1985), 358.
 . Po-chia Hsia, “Jews as Magicians in Reformation Germany,” in Sander L. Gilman and Steven T. Katz, Anti-Semitism in Times of Crisis (New York: New York University Press, 1991), 124-125.
 Carter Lindberg, “Tainted Greatness: Luther’s Attitudes Toward Judaism and Their Historical Reception,” in Nancy A Harrowitz (ed.), Tainted Greatness: Antisemitism and Cultural Heroes (Philadelphia: Temple University Press, 1994), 22.
 Catholic Encyclopedia, Johann Eck entry.
 Catholic Encyclopedia, Luther entry.
 Catholic Encyclopedia, entry on the History of the Jews.