Mitzvah goreret mitzvah
Amazingly, Astruc, though a Christian, had good yichus, coming fromthe same medieval Jewish family which produced rabbi Abba Mari of Lunel, AKA The Yarchi. The Yarchi, of course, being famous for the cherem of Montpellier. Here's what Wikipedia has to say about the controversy:
Abba Mari possessed considerable Talmudic knowledge and some poetical talent; but his zeal for the Law made him an agitator and a persecutor of all the advocates of liberal thought. Being himself without sufficient authority, he appealed in a number of letters, afterward published under the title of Minḥat Ḳenaot (Jealousy Offering), to Solomon ben Adret of Barcelona, the most influential rabbi of the time, to use his powerful authority to check the source of evil by hurling his anathema against both the study of philosophy and the allegorical interpretations of the Bible, which did away with all belief in miracles. Ben Adret, while reluctant to interfere in the affairs of other congregations, was in perfect accord with Abba Mari as to the danger of the new rationalistic systems, and advised him to organize the conservative forces in defense of the Law. Abba Mari, through Ben Adret's aid, obtained allies eager to take up his cause, among whom were Don Bonafoux Vidal of Barcelona and his brother, Don Crescas Vidal, then in Perpignan. The proposition of the latter to prohibit, under penalty of excommunication, the study of philosophy and any of the sciences except medicine, by one under thirty years of age, met with the approval of Ben Adret. Accordingly, Ben Adret addressed to the congregation of Montpellier a letter, signed by fifteen other rabbis, proposing to issue a decree pronouncing the anathema against all those who should pursue the study of philosophy and science before due maturity in age and in rabbinical knowledge. On a Sabbath in September, 1304, the letter was to be read before the congregation, when Jacob Machir Don Profiat Tibbon, the renowned astronomical and mathematical writer, entered his protest against such unlawful interference by the Barcelona rabbis, and a schism ensued. Twenty-eight members signed Abba Mari's letter of approval; the others, under Tibbon's leadership, addressed another letter to Ben Adret, rebuking him and his colleagues for condemning a whole community without knowledge of the local conditions. Finally, the agitation for and against the liberal ideas brought about a schism in the entire Jewish population in southern France and Spain.
Encouraged, however, by letters signed by the rabbis of Argentière and Lunel, and particularly by the support of Kalonymus ben Todros, the nasi of Narbonne, and of the eminent Talmudist Asheri of Toledo, Ben Adret issued a decree, signed by thirty-three rabbis of Barcelona, excommunicating those who should, within the next fifty years, study physics or metaphysics before their thirtieth year of age (basing his action on the principle laid down by Maimonides, Guide for the Perplexed part one chapter 34), and had the order promulgated in the synagogue on Sabbath, July 26, 1305. When this heresy-decree, to be made effective, was forwarded to other congregations for approval, the friends of liberal thought, under the leadership of the Tibbonites, issued a counter-ban, and the conflict threatened to assume a serious character, as blind party zeal (this time on the liberal side) did not shrink from asking the civil powers to intervene. But an unlooked-for calamity brought the warfare to an end. The expulsion of the Jews from France by Philip IV ("the Fair"), in 1306, caused the Jews of Montpellier to take refuge, partly in Provence, partly in Perpignan and partly in Majorca. Consequently, Abba Mari removed first to Arles, and, within the same year, to Perpignan, where he finally settled and disappeared from public view. There he published his correspondence with Ben Adret and his colleagues.