Max Bruch died in 1920, thirteen years before the Nazi party took power in Germany, and so never lived to see what became of his most famous piece under that regime. Nazi cultural authorities, purging German musical life of Jewish composers and Jewish-associated music, encountered Kol Nidrei's evident depth of feeling for a Jewish liturgical theme and drew the only conclusion their own ideology permitted them to draw: that no Christian composer could have written something so moving about a Jewish subject, and that Bruch must therefore have been secretly Jewish himself.
The reasoning was false at every step, and the record shows it plainly. Bruch was raised Protestant, given the explicitly Christian middle name Christian, and no documented ancestry connects him to Jewish descent on any side. What actually explains the piece is more mundane and, in its way, more interesting: a genuine personal friendship with a Berlin cantor in the late 1870s gave Bruch access to melodies he found beautiful enough to want to preserve and share, exactly as he said himself at the time. None of that mattered to authorities working from racial theory rather than biography. Bruch's music, Kol Nidrei above all, was forbidden on German airwaves for the duration of the regime.
The irony did not go unnoticed once the war ended and the ban lifted. A piece written as one outsider's tribute to a tradition not his own had been silenced by a regime that assumed genuine cross-tradition admiration of that kind was itself impossible, then vindicated by the simple fact of its own survival past the ban.