Documents have recently come to light proving that the youngest son of the founder of the Chabad movement, Rabbi Shneur Zalman of Liadi, Russia, converted to Catholicism. For 180 years, the conversion of Moshe Zalmanovitch (son of Zalman) has been difficult for Chabad hassidim and the hassidic world in general to accept. Now, it will be difficult to ignore.Moshe, btw, was always and genuinely known to be mentally unstable.
Rumors of the conversion of Moshe and conversions in other Hassidic families were rife in the 19th century, fueled by members of the Enlightenment who, in spite of their world view, nevertheless excoriated such moves. Chabad denied the rumors vehemently over the years, presenting alternative versions of the life of the rabbi's youngest son, a married father of four. But documents, copies of which are in Jerusalem, prove the rumors true. The original documents are located in the national historical archives in Minsk, the capital of Belarussia...
One of the most important documents is a letter written by Moshe on July 1, 1820. It was addressed to a Polish priest named Siodlovsky, in the Polish city of Ulla, where Moshe lived after his marriage.
The 36-year-old Moshe wrote he had long sought to become Roman Catholic.
He said the Jews had tried to prevent him from doing so by watching him constantly, beating him and threatening him. However, he wrote: "I have remained steadfast in my desire to take upon myself the true faith of Jesus Christ, to which the holy books and all the prophets testify."
The declaration was made before Christian witnesses, officers and clerks, whose names and occupations are noted in the document. They signed, certifying that the writer of the declaration was "of sound mind."
Thus, Moshe son of Zalman became Leon Yoleivitch.
The truth is that his conversion is only embarrassing / something to be ashamed of / something that can harm your movement if that's how you treat it. The best strategy here for Lubavitchers would be to acknowledge it, shrug, and move on. Still, Lubavitchers are, not surprisingly, claiming the documents are fake (although I would like to hear an answer to point number one). Ha'aretz wrote a long and interesting article about all this last year if you want to read more.