You can understand why the Church had suspicion of conversos.
Many Jewish converts to Christianity around the time of the Reformation pushed the humanist approach to religion. That approach is safer for Jews.
Even when they convert to another religion, many Jews are intent on making the world more hospitable for Jews.
John Connelly writes for the Forward in 2012:
As I discovered while researching my recently published book, “From Enemy to Brother: The Revolution in Catholic Teaching on the Jews, 1933–1965,” these experts did not begin their work in the 1960s. From outposts in Austria and Switzerland, several had tried to formulate Catholic arguments against anti-Semitism under the shadow of Nazism three decades earlier. They were as unrepresentative of Catholicism as one can imagine. Not only were they, Central Europeans, brave enough to stand up to Hitler when it counted, but they mostly had not been born Catholic. The Catholics who helped bring the church to recognition of the continuing sanctity of the Jewish people were converts, many of them from Jewish families.
Most important was Johannes Oesterreicher, born in 1904 into the home of the Jewish veterinarian Nathan and his wife, Ida, in Stadt-Liebau, a German-language community in northern Moravia. As a boy, he took part in Zionist scouting and acted as elected representative of the Jews in his high school, but then, for reasons that remain inexplicable (he later said he ”fell in love with Christ”), Oesterreicher took an interest in Christian writings (Cardinal Newman, Kierkegaard and the Gospels themselves), and under the influence of a priest later martyred by the Nazis (Max Josef Metzger) he became a Catholic and then a priest. In the early 1930s he took over the initiative of the Diocese of Vienna for converting Jews, hoping to bring family and friends into the church. In this his success was limited. Where he had an impact was in gathering other Catholic thinkers to oppose Nazi racism. To his shock, Oesterreicher found this racism entering the work of leading Catholic thinkers, who taught that Jews were racially damaged and therefore could not receive the grace of baptism. His friends in this endeavor included fellow converts like philosopher Dietrich von Hildebrand and the theologian Karl Thieme and political philosopher Waldemar Gurian. In 1937, Gurian, Oesterreicher and Thieme penned a Catholic statement on the Jews, arguing, against the racists, that Jews carried a special holiness. Though it constituted orthodox teaching, not a single bishop (let alone the Vatican) signed on.
Oesterreicher escaped Austria when the Nazis entered, in 1938, and continued work from Paris, broadcasting German-language sermons into the Reich, informing Catholics that Hitler was an “unclean spirit” and the “antipode in human form,” and describing Nazi crimes committed against Jews and Poles. In the spring of 1940 he barely eluded an advance team of Gestapo agents, and via Marseille and Lisbon he made his way to New York City and ultimately Seton Hall University, where he became the leading expert on relations with Jews in America’s Catholic Church.
Oesterreicher gradually abandoned his “missionary” approach to the Jews and increasingly called his work ecumenical. He and like-minded Christians tried to figure out how to ground their belief in continued vocation of Jewish people in Christian scripture. If the battle before the war was against the superficial assumptions of Nazi racism, after the war it took aim at the deeply rooted beliefs of Christian anti-Judaism. In the former period, the converts argued that, yes, Jews can be baptized. In the second period, even if they continued to believe that Jews must be baptized to escape the curse of rejecting Christ, these thinkers began pondering the nature of the supposed curse.
If history was a series of trials sent to punish the Jews for failing to accept Christ, then what meaning did Auschwitz have? Were the Nazis instruments of God’s will, meant to make the Jews finally turn to Christ? To answer yes to this question was obscene, but it was the only answer Catholic theology provided as of 1945. In the years that followed, the converts had to stage a revolution in a church that claimed to be unchanging. They did so by shifting church teaching to Paul’s letter to the Romans, chapters 9–11, where the Apostle, without speaking of baptism or conversion, proclaims that the Jews remain “beloved of God” and that “all Israel will be saved.”
Like Oesterreicher, the thinkers who did the intellectual work that prepared this revolution were overwhelmingly converts. Soon after the war, Thieme joined with concentration camp survivor Gertrud Luckner to publish the Freiburger Rundbrief in southwest Germany, where they made crucial theological breakthroughs on the path to conciliation with the Jews. In Paris, the Rev. Paul Démann, a converted Hungarian Jew, began publishing the review Cahiers Sioniens and, with the help of fellow converts Geza Vermes and Renée Bloch, refuted the anti-Judaism in Catholic school catechisms.
In 1961, Oesterreicher was summoned for work in the Vatican II committee tasked with the “Jewish question,” which became the most difficult issue to face the bishops. At one critical moment in October 1964, priests Gregory Baum and Bruno Hussar joined Oesterreicher in assembling what became the final text of the council’s decree on the Jews, voted on by the bishops a year later. Like Oesterreicher, Baum and Hussar were converts of Jewish background.
They were continuing a trend going back to the First Vatican Council in 1870, when the brothers Lémann — Jews who had become Catholics and priests — presented a draft declaration on relations between the church and Jews, stating that Jews “are always very dear to God” because of their fathers and because Christ has issued from them “according to the flesh.” Without converts to Catholicism, it seems, the Catholic Church would never have “thought its way” out of the challenges of racist anti-Judaism.
The high percentage of Jewish converts like Oesterreicher among Catholics who were opposed to anti-Semitism makes sense: In the 1930s they were targets of Nazi racism who could not avoid the racism that had entered the church. In their opposition, they were simply holding their church to its own universalism. But by turning to long-neglected passages in St. Paul’s letter to the Romans, they also opened the mind of the church to a new appreciation of the Jewish people.
